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Closed 9 years ago.
Here are the estimates the system should handle:
3000+ end users
150+ offices around the world
1500+ concurrent users at peak times
10.000+ daily updates
4-5 commits per second
50-70 transactions per second (reads/searches/updates)
This will be internal only business application, dedicated to help shipping company with worldwide shipment management.
What would be your technology choice, why that choice and roughly how long would it take to implement it? Thanks.
Note: I'm not recruiting. :-)
So, you asked how I would tackle such a project. In the Smalltalk world, people seem to agree that Gemstone makes things scale somewhat magically.
So, what I'd really do is this: I'd start developing in a simple Squeak image, using SandstoneDB. Then, this moment would come where a single image begins being too slow.
GemStone then takes care of copying your public objects (those visible from a certain root) back and forth between all instances. You get sessions and enhanced query functionalities, plus quite a fast VM.
It shares data with C, Java and Ruby.
In fact, they have their own VM for ruby, which is also worth a look.
wikipedia manages much more demanding requirements with MySQL
Your volumes are significant but not likely to strain any credible RDBMS if programmed efficiently. If your team is sloppy (i.e., casually putting SQL queries directly into components which are then composed into larger components), you face the likelihood of a "multiplier" effect where one logical requirement (get the data necessary for this page) turns into a high number of physical database queries.
So, rather than focussing on the capacity of your RDBMS, you should focus on the capacity of your programmers and the degree to which your implementation language and environment facilitate profiling and refactoring.
The scenario you propose is clearly a 24x7x365 one, too, so you should also consider the need for monitoring / dashboard requirements.
There's no way to estimate development effort based on the needs you've presented; it's great that you've analyzed your transactions to this level of granularity, but the main determinant of development effort will be the domain and UI requirements.
Choose the technology your developers know and are familiar with. All major technologies out there will handle such requirements with ease.
Your daily update numbers vs commits do not add up. Four commits per second = 14,400 per hour.
You did not mention anything about expected database size.
In any case, I would concentrate my efforts on choosing a robust back end like Oracle, Sybase, MS etc. This choice will make the most difference in performance. The front end could either be a desktop app or WEB app depending on needs. Since this will be used in many offices around the world, a WEB app might make the most sense.
I'd go with MySQL or PostgreSQL. Not likely to have problems with either one for your requirements.
I love object-databases. In terms of commits-per-second and database-roundtrip, no relational database can hold up. Check out db4o. It's dead easy to learn, check out the examples!
As for the programming language and UI framework: Well, take what your team is good at. Dynamic languages with fewer meta-time wasting will probably save time.
There is not enough information provided here to give a proper recommendation. A little more due diligence is in order.
What is the IT culture like? Do they prefer lots of little servers or fewer bigger servers or big iron? What is their position on virtualization?
What is the corporate culture like? What is the political climate like? The open source offerings may very well handle the load but you may need to go with a proprietary vendor just because they are already used to navigating the political winds of a large company. Perception is important.
What is the maturity level of the organization? Do they already have an Enterprise Architecture team in place? Do they even know what EA is?
You've described the operational side but what about the analytical side? What OLAP technology are they expecting to use or already have in place?
Speaking of integration, what other systems will you need to integrate with?
Related
i am currently working on an existing infrastructure where i have about a 1000 customer sites connected to about 5 different hubs. A customer site may connect to one or two hubs to ensure reliability but each customer site is connected to at least one hub. I want to ensure if the current system is the best or can be optimised to have better connection from customer sites to hubs, to help improve connectivity and reliability. Can you suggest good Optimisation Algorithms to look into?. Thank you
Sounds like you're doing some variation of the Facility Problem.
This is a well-known problem, and while there are algorithms that can solve for the global optimum (Djiskra's Algorithm, or other variants of Dynamic Programming), they do not scale well (i.e. you run into the curse of dimensionality). You could try this, but 1000 sounds already pretty big (depends on your exact problem formulation though).
I'd recommend taking a look at this coursera mooc Discrete Optimization. You don't have to take the whole course, but in the "Assignments" section of the video lectures, he also explains a variant of the Facility problem, some possible approaches to think about, and once you've decided which one you want to use, you can look deeper into that particular approach.
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Closed 10 years ago.
Apart from graphical features, online games should have a simple Relational Database structure. I am curious what database do online games like Farmville and MafiaWars use?
Is it practical to use SQL based databases for such programs with such frequent writes ?
If not, how could one store the relational dependence of users in these games?
EDIT: As pointed, they use NOSQL databases like Couchbase. NOSQL is fast with good cuncurrency (which is really needed here); but the sotrage size is much larger (due to key/value structure).
1. Does't it slow down the system (as we need to read large database files from the disk)?
2. We will be very limited as we do not have SQL's JOIN to connected different sets of data.
These databases scale to about 500,000 operations per second, and they're massively distributed. Zynga still uses SQL for logs, but for game data, they presently use code that is substantially the same as Couchbase.
“Zynga’s objective was simple: we needed a database that could keep up with the challenging demands of our games while minimizing our average, fully-loaded cost per database operation – including capital equipment, management costs and developer productivity. We evaluated many NoSQL database technologies but all fell short of our stringent requirements. Our membase development efforts dovetailed with work being done at NorthScale and NHN and we’re delighted to contribute our code to the open source community and to sponsor continuing efforts to maintain and enhance the software.” - Cadir Lee, Chief Technology Officer, Zynga
To Answer your edit:
You can decrease storage size by using a non key=>value storage like MongoDB. This does still have some overhead but less than trying to maintain a key=>value store.
It does not slow down the system terribly since quite a few NoSQL products are memory mapped which means that unlike SQL it doesn't go directly to disk but instead to a fsync queue that then writes to disk when it is convient to. For those NoSQL solutions which are not memory mapped they have extremely fast read/write speeds and it is normally a case of trade off between the two.
As for JOINs, it is a case of arranging your schema in such a manner that you can avoid huge joins. Small joins to join say, a user with his score record are fine but aggregated joins will be a problem and you will need to find other ways around this. There are numerous solutions provided by many user groups of various NoSQL products.
The database they use has been reported to be Membase. It's open source, and one of the many nosql databases.
In January 2012, Membase became Couchbase, and you can download it here if you want to give it a try.
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Closed 10 years ago.
I'm curious about a certain job title, that of "senior developer with a specialty in optimisation." It's not the actual title but that's essentially what it would be. What would this mean in the gaming industry in terms of knowledge and skills? I would assume basic stuff like
B-trees
Path finding
Algorithmic analysis
Memory management
Threading (and related topics like thread safety, atomicity, etc)
But this is only me conjecturing. What would be the real-life (and academic) basic knowledge required for such a job?
I interviewed for such a position a few years ago at one of the Big North American game studios.
The job required a lot of deep pipeline assembly programming, arithmetic optimization algorithms (think Duff's Device, branchless ifs), compile-time computation (SWAR), meta-template programming, computation of many values at once in parallel in very large registers (I forget the name for that)... You'll need to be solid on operating system fundementals, low level system operations, linear algebra, and C++ especially templates. You'll also become very familiar with the peculiar architecture of the PlayStation3, and probably be involved in developing libraries for that environment that the company's game teams will build on top of.
Generally I concur with Ether's post; this will typically be more about low-level optimisation than algorithmic stuff. Knowing good algorithms comes in handy, but there are many cases in games where you prefer the O(N) solution over the O(logN) solution because the first is far friendlier on the cache and requires less memory management. So you need a more holistic knowledge.
Perhaps on a more general level, the job may want to know if you can do some or all of the following:
use a CPU profiler (eg. VTune, CodeAnalyst) in both sampling and call graph mode;
use graphical profilers (eg. Microsoft Pix, NVPerfHud)
write your own profiling/timer code and generate useful output with it;
rewrite functions to remove dynamic memory allocations;
reorganise and reduce data to be more cache-friendly;
reorganise data to make it more SIMD-friendly;
edit graphics shaders to use fewer and cheaper instructions;
...and more, I'm sure.
This is a lot like my job actually. Real-life knowledge that would be practical for this:
Experience in using profilers of all kinds to locate bottlenecks.
Experience and skill in determining the reason those bottlenecks exist.
Good understanding of CPU caches, virtual memory, and common bottlenecks such as load-hit-store penalties, L2 misses, floating point code, etc.
Good understanding of multithreading and both lockless and locking solutions.
Good understanding of HLSL and graphics programming, including linear algebra.
Good understanding of SIMD techniques and the specific SIMD interfaces on relevant hardware (paired singles, VMX, SSE/MMX).
Good understanding of the assembly language used on relevant hardware. If writing assembly, a good understanding of instruction pairing, branch prediction, delay slots (if applicable), and any and all applicable stalls on the target platform.
Good understanding of the compilation and linking process, binary formats used on the target hardware, and tools to manipulate all of the above (including available compiler flags and optimizations).
Every once in a while people ask how to become good at low-level optimization. There are a few good sources of info, mostly proprietary, but I think it generally comes down to experience.
This is one of those "if you got it you know it" type of things. It's hard to list out specifics, and some studios will have different criteria than others.
To put it simply, the 'Senior Developer' part means you've been around the block; you have multiple years of experience in which you've excelled and have shipped games. You should have a working knowledge of a wide range of topics, with things such as memory management high up the list.
"Specialty in Optimization" essentially means that you know how to make a game run faster. You've already spent a significant amount of time successfully optimizing games which have shipped. You should have a wide knowledge of algorithms, 3d rendering (a lot of time is spent rendering), cpu intrinsics, memory management, and others. You should also typically have an in depth knowledge of the hardware you'd be working on (optimizing PS3 can be substantially different than optimizing for PC).
This is at best a starting point for understanding. The key is having significant real world experience in the topic; at a senior level it should preferably be from working on titles that have shipped.
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Closed 10 years ago.
I would like to track metrics that can be used to improve my team’s software development process, improve time estimates, and detect special case variations that need to be addressed during the project execution.
Please limit each answer to a single metric, describe how to use it, and vote up the good answers.
(source: osnews.com)
ROI.
The total amount of revenue brought in by the software minus the total amount of costs to produce the software. Breakdown the costs by percentage of total cost and isolate your poorest performing and most expensive area in terms of return-on-investment. Improve, automate, or eliminate that problem area if possible. Conversely, find your highest return-on-investment area and find ways to amplify its effects even further. If 80% of your ROI comes from 20% of your cost or effort, expand that particular area and minimize the rest by comparison.
Costs will include payroll, licenses, legal fees, hardware, office equipment, marketing, production, distribution, and support. This can be done on a macro level for a company as whole or a micro level for a team or individual. It can also be applied to time, tasks, and methods in addition to revenue.
This doesn't mean ignore all the details, but find a way to quantify everything and then concentrate on the areas that yield the best (objective) results.
Inverse code coverage
Get a percentage of code not executed during a test. This is similiar to what Shafa mentioned, but the usage is different. If a line of code is ran during testing then we know it might be tested. But if a line of code has not been ran then we know for sure that is has not been tested. Targeting these areas for unit testing will improve quality and takes less time than auditing the code that has been covered. Ideally you can do both, but that never seams to happen.
"improve my team’s software development process": Defect Find and Fix Rates
This relates to the number of defects or bugs raised against the number of fixes which have been committed or verified.
I'd have to say this is one of the really important metrics because it gives you two things:
1. Code churn. How much code is being changed on a daily/weekly basis (which is important when you are trying to stabilize for a release), and,
2. Shows you whether defects are ahead of fixes or vice-versa. This shows you how well the development team is responding to defects raised by the QA/testers.
A low fix rate indicates the team is busy working on other things (features perhaps). If the bug count is high, you might need to get developers to address some of the defects.
A low find rate indicates either your solution is brilliant and almost bug free, or the QA team have been blocked or have another focus.
Track how long is takes to do a task that has an estimate against it. If they were well under, question why. If they are well over, question why.
Don't make it a negative thing, it's fine if tasks blow out or were way under estimated. Your goal is to continually improve your estimation process.
Track the source and type of bugs that you find.
The bug source represents the phase of development in which the bug was introduced. (eg. specification, design, implementation etc.)
The bug type is the broad style of bug. eg. memory allocation, incorrect conditional.
This should allow you to alter the procedures you follow in that phase of development and to tune your coding style guide to try to eliminate over represented bug types.
Velocity: the number of features per given unit time.
Up to you to determine how you define features, but they should be roughly the same order of magnitude otherwise velocity is less useful. For instance, you may classify your features by stories or use cases. These should be broken down so that they are all roughly the same size. Every iteration, figure out how many stories (use-cases) got implemented (completed). The average number of features/iteration is your velocity. Once you know your velocity based on your feature unit you can use it to help estimate how long it will take to complete new projects based on their features.
[EDIT] Alternatively, you can assign a weight like function points or story points to each story as a measure of complexity, then add up the points for each completed feature and compute velocity in points/iteration.
Track the number of clones (similar code snippets) in the source code.
Get rid of clones by refactoring the code as soon as you spot the clones.
Average function length, or possibly a histogram of function lengths to get a better feel.
The longer a function is, the less obvious its correctness. If the code contains lots of long functions, it's probably a safe bet that there are a few bugs hiding in there.
number of failing tests or broken builds per commit.
interdependency between classes. how tightly your code is coupled.
Track whether a piece of source has undergone review and, if so, what type. And later, track the number of bugs found in reviewed vs. unreviewed code.
This will allow you to determine how effectively your code review process(es) are operating in terms of bugs found.
If you're using Scrum, the backlog. How big is it after each sprint? Is it shrinking at a consistent rate? Or is stuff being pushed into the backlog because of (a) stuff that wasn't thought of to begin with ("We need another use case for an audit report that no one thought of, I'll just add it to the backlog.") or (b) not getting stuff done and pushing it into the backlog to meet the date instead of the promised features.
http://cccc.sourceforge.net/
Fan in and Fan out are my favorites.
Fan in:
How many other modules/classes use/know this module
Fan out:
How many other modules does this module use/know
improve time estimates
While Joel Spolsky's Evidence-based Scheduling isn't per se a metric, it sounds like exactly what you want. See http://www.joelonsoftware.com/items/2007/10/26.html
I especially like and use the system that Mary Poppendieck recommends. This system is based on three holistic measurements that must be taken as a package (so no, I'm not going to provide 3 answers):
Cycle time
From product concept to first release or
From feature request to feature deployment or
From bug detection to resolution
Business Case Realization (without this, everything else is irrelevant)
P&L or
ROI or
Goal of investment
Customer Satisfaction
e.g. Net Promoter Score
I don't need more to know if we are in phase with the ultimate goal: providing value to users, and fast.
number of similar lines. (copy/pasted code)
improve my team’s software development process
It is important to understand that metrics can do nothing to improve your team’s software development process. All they can be used for is measuring how well you are advancing toward improving your development process in regards to the particular metric you are using. Perhaps I am quibbling over semantics but the way you are expressing it is why most developers hate it. It sounds like you are trying to use metrics to drive a result instead of using metrics to measure the result.
To put it another way, would you rather have 100% code coverage and lousy unit tests or fantastic unit tests and < 80% coverage?
Your answer should be the latter. You could even want the perfect world and have both but you better focus on the unit tests first and let the coverage get there when it does.
Most of the aforementioned metrics are interesting but won't help you improve team performance. Problem is your asking a management question in a development forum.
Here are a few metrics: Estimates/vs/actuals at the project schedule level and personal level (see previous link to Joel's Evidence-based method), % defects removed at release (see my blog: http://redrockresearch.org/?p=58), Scope creep/month, and overall productivity rating (Putnam's productivity index). Also, developers bandwidth is good to measure.
Every time a bug is reported by the QA team- analyze why that defect escaped unit-testing by the developers.
Consider this as a perpetual-self-improvement exercise.
I like Defect Resolution Efficiency metrics. DRE is ratio of defects resolved prior to software release against all defects found. I suggest tracking this metrics for each release of your software into production.
Tracking metrics in QA has been a fundamental activity for quite some time now. But often, development teams do not fully look at how relevant these metrics are in relation to all aspects of the business. For example, the typical tracked metrics such as defect ratios, validity, test productivity, code coverage etc. are usually evaluated in terms of the functional aspects of the software, but few pay attention to how they matter to the business aspects of software.
There are also other metrics that can add much value to the business aspects of the software, which is very important when an overall quality view of the software is looked at. These can be broadly classified into:
Needs of the beta users captured by business analysts, marketing and sales folks
End-user requirements defined by the product management team
Ensuring availability of the software at peak loads and ability of the software to integrate with enterprise IT systems
Support for high-volume transactions
Security aspects depending on the industry that the software serves
Availability of must-have and nice-to-have features in comparison to the competition
And a few more….
Code coverage percentage
If you're using Scrum, you want to know how each day's Scrum went. Are people getting done what they said they'd get done?
Personally, I'm bad at it. I chronically run over on my dailies.
Perhaps you can test CodeHealer
CodeHealer performs an in-depth analysis of source code, looking for problems in the following areas:
Audits Quality control rules such as unused or unreachable code,
use of directive names and
keywords as identifiers, identifiers
hiding others of the same name at a
higher scope, and more.
Checks Potential errors such as uninitialised or unreferenced
identifiers, dangerous type casting,
automatic type conversions, undefined
function return values, unused
assigned values, and more.
Metrics Quantification of code properties such as cyclomatic
complexity, coupling between objects
(Data Abstraction Coupling), comment
ratio, number of classes, lines of
code, and more.
Size and frequency of source control commits.
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Closed 10 years ago.
I really like ORM as compared to store procedure, but one thing that I afraid is that ORM could be slow, because of layers and layers of abstraction. Will using ORM slow down my application? Or does it matter?
Yes, it matters. It is using more CPU cycles and consequently slowing your application down. Hear me out though...
But, consider this: what is more expensive? Server hardware or another programmer? Server hardware, generally, is cheaper than hiring another team of programmers. So, while ORM may be costing you CPU cycles, you need one less programmer to manage your SQL queries, often resulting in a lower net cost.
To determine if it's worth it for you, calculate or determine how many hours you saved by using an ORM. Then, figure out how much money you spent on the server to support ORM. Multiply the hours you saved by your hourly rate and compare to the server cost.
Of course, whether an ORM actually saves you time is a whole another debate...
Is ORM slow?
Not inherently. Some heavyweight ORMs can add a general drag to things but we're not talking orders of magnitude slowdown.
What does make ORM slow is naïve usage. If you're using an ORM because it looks easy and you don't know how the underlying relational data model works, you can easily write code that seems reasonable to an OO programmer, but will murder performance.
ORM is a handy tool, but you need the lower-level understanding (that usually comes from writing SQL queries) to go with it.
Does it matter?
If you end up performing a looped query for each of thousands of entities at once, instead of a single fast join, then certainly it can.
ORM's are slower and do add overhead to applications (unless you specifically know how to get around these problems, which is not very common). The database is the most critical element and Web applications should be designed around it.
Many OOP frameworks using Active Record or ORMs, developers in general - treat the database as an unimportant afterthought and tend to look at it as something they don't really need to learn. But performance and scalability usually suffer as the db is heavily taxed!
Many large scale web apps have fallen flat, wasting millions and months to years of time because they didn't recognize the importance of the database. Hundreds of concurrent users and tables with millions of records require database tuning and optimization. But I believe the problem is noticeable with a few users and less data.
Why are developers so afraid to learn proper SQL and tuning measures when it's the key to performance?
In a Windows Mobile 5 project against using SqlCe, I went from using hand-coded objects to code generated (CodeSmith) objects using an ORM template. In the process all my data access used CSLA as a base layer.
The straight conversion improved my performance by 32% in local testing, almost all of it a result of better access methods.
After that change, we adjusted the templates (after seeing some SqlCe performance stuff at PDC by Steve Lasker) and in less then 20 minutes, our entire data layer was greatly improved, our average 'slow' calls went from 460ms to ~20ms. The cool part about the ORM stuff is that we only had to implement (and unit test) these changes once and all the data access code got changed. It was an amazing time saver, we maybe saved 40 hours or more.
The above being said, we did lose some time by taking out a bunch of 'waiting' and 'progress' dialogs that were no longer needed.
I have used a few of the ORM tools, and I can recommend two of them:
.NET Tiers
CSLA codegen templates
Both of them have performed quite nicely and any performance loss has not been noticeable.
I've always found it doesn't matter. You should use whatever will make you the most productive, responsive to changes, and whatever is easiest to debug and maintain.
Most applications never need enough load for the difference between ORM and SPs to noticeable. And there are optimizations to make ORM faster.
Finally, a well-written app will have its data access seperated from everything else so that in the future switching from ORM to whatever would be possible.
Is ORM slow?
Yes ( compared with stored procedures )
Does it matter?
No ( except your concern is speed )
I think the problem is many people think of ORM as a object "trick" to databases, to code less or simplify SQL usage, while in reality is .. well an Object - To Relational ( DB ) - Mapping.
ORM is used to persist your objects to a relational database manager system, and not ( just ) to substitute or make SQL easier ( although it make a good job at that too )
If you don't have a good object model, or you're using to make reports, or even if you're just trying to get some information, ORM is not worth it.
If in the other hand you have a complex system modeled through objects were each one have different rules and they interact dynamically and you your concern is persist that information into the database rather than substitute some existing SQL scripts then go for ORM.
Yes, ORM will slow down your application. By how much depends on how far the abstraction goes, how well your object model maps to the database, and other factors. The question should be, are you willing to spend more developer time and use straight data access or trade less dev time for slower runtime performance.
Overall, the good ORMs have little overhead and, by and large, are considered well worth the trade off.
Yes, ORMs affect performance, whether that matters ultimately depends on the specifics of your project.
Programmers often love ORM because they like the nice front-end cding environments like Visual Studio and dislike coding raw SQL with no intellisense, etc.
ORMs have other limitations besides a performance hit--they also often do not do what you need 100% of the time, add the complexity of an additional abstraction layer that must be maintained and re-established every time chhnges are made, there are also caching issues to be dealt with.
Just a thought -- if the database vendors would make the SQL programming environment as nice as Visual Studio, and provide a more natural linkage between the db code and front-end code, we wouldn't need the ORMs...I guess things may go in that direction eventually.
Obvious answer: It depends
ORM does a good job of insulating a programmer from SQL. This in effect substitutes mediocre, computer generated queries for the catastrophically bad queries a programmer might give.
Even in the best case, an ORM is going to do some extra work, loading fields it doesn't need to, explicitly checking constraints, and so forth.
When these become a bottle-neck, most ORM's let you side-step them and inject raw SQL.
If your application fits well with objects, but not quite so easily with relations, then this can still be a win. If instead your app fits nicely around a relational model, then the ORM represents a coding bottleneck on top of a possible performance bottleneck.
One thing I've found to be particularly offensive about most ORM's is their handling of primary keys. Most ORM's require pk's for everything they touch, even if there is no concievable use for them. Example: Authors should have pk's, Blog posts SHOULD have pk's, but the links (join table) between authors and posts not.
I have found that the difference between "too slow" and "not too much slower" depends on if you have your ORM's 2nd level (SessionFactory) cache enabled. With it off it handles fine under development load, but will crush your system under mild production load. After turning on the 2nd Level cache the server handled the expected load and scaled nicely.
ORM can get an order of magnitude slower, not just on the grount=s of wasting a lot of CPU cycles on it's own but also using much more memeory which then has to be GC-d.
Much worse that that however is that the is no standard for ORM (unlike SQL) and that my and large ORM-s use SQL vary inefficiently so at the end of the day you still have to dig into SQL to fix per issues and every time an ORM makes a mess and you have to debug it. Meaning that you haven't gained anything at all.
It's terribly immature technology for real production-level applications. Very problematic things are handling indexes, foreign keys, tweaking tables to fit object hierarchies and terribly long transactions, which means much more deadlocks and repeats - if an ORM knows hows to handle that at all.
It actually makes servers less scalable which multiplies costs but these costs don't get mentioned at the begining - a little inconvenient truth :-) When something uses transactions 10-100 times bigger than optimal it becomes impossible to scale SQL side at all. Talking about serious systems again not home/toy/academic stuff.
An ORM will always add some overhead because of the layers of abstraction but unless it is a poorly designed ORM that should be minimal. The time to actually query the database will be many times more than the additional overhead of the ORM infrastructure if you are doing it correctly, for example not loading the full object graph when not required. A good ORM (nHibernate) will also give you many options for the queries run against the database so you can optimise as required as well.
Using an ORM is generally slower. But the boost in productivity you get will get your application up and running much faster. And the time you save can later be spent finding the portions of your application that are causing the biggest slow down - you can then spend time optimizing the areas where you get the best return on your development effort. Just because you've decided to use an ORM doesn't mean you can't use other techniques in the sections of code that can really benefit from it.
An ORM can be slower, but this is offset by their ability to cache data, therefore however fast the alternative, you can't get much faster than reading from memory.
I never really understood why people think that this is slower or that is slower... get a real machine I say. I have had mixed results... I've seen where execution time for a stored procedure is much slower than ORM and vise versa.. But in both cases the performance was due to difference in hardware.