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发信人: golf (..), 信区: Linux
标 题: 关于Mysql在FreeBSD和Linux上的性能话题
发信站: BBS 荔园晨风站 (Sun Nov 28 03:39:23 1999), 转信
Some chat about Linux VS FreeBSD on Mysql From Mysql Archive:
Original Message is talk about chose FreeBSD or Linux for
a mysql box of single processor. Here is some chat:
...
You can't turn off asynchronous writes on Linux! this is bad but I've run
production Linux systems for years without problems.. When kernel 2.4
comes out with the journaling file system then there'd be a really
compelling advantage for Linux over BSD. But until then.. BSD has a
reputation for being more stable than Linux under load.
Also: because under Linux a thread is a process, you are limited by the
number of processes allowed (512 max, 3900+ with patches) so if you're
using MySQL you are limited as to the maximum number of connections
possible if you're using Linux. OTOH BSD uses a userlevel thread
implementation AFAIK (except really new FreeBSD releases) so the Linux
implementation would perform better on SMP boxes.
...
> I thought the MIT-pthreads worked around this problem?
But MIT-pthreads are user-level threads. So they all run within one kernel
context and so cannot take advantage of multiple processors.
...
(Orlando Andico)
...
Assuming capable operating systems, 95% of the performance is going to be
based on the hardware, especially I/O capabilities. Of course, there are
edge cases where one of the two has good (or bad) support for a particular
SCSI card, or Ethernet card, or whatever, which is something to stay away
from.
Various people have claimed that Linux is the better performer, for various
reasons, but in our testing with heavily loaded servers, we've found it to
be pretty much a wash. Perhaps Linux is5% faster when overloaded (but on
the flip side, we found that when Linux was overloaded, shell sessions were
very slow, while when FreeBSD is overloaded, the shell is still snappy. It
may be that the 5% is entirely due to various tuning decisions, as opposed
to innate advantages one way or the other).
...
At one point, I was VERY concerned about FreeBSD using userland threads and
Linux using lightweight tasks. Handling I/O blocking between tasks is a
well-understood problem, and I wondered if seperate tasks would allow for
better throughput than userland threads. At least with FreeBSD3.1, I have
no evidence of this being a problem. I still would be more comfortable if I
had the option of using kernel threads, but they're not there, yet.
As far as kernel patches to up things like process max and the like - now's
the time. Once the server is up and in use, it'll be harder to take it down
to do things like increase the max processes, or max sockets, or max file
descriptors, or whatever else you want to do to it.
(Later, scott)
...
Probably the performance will be about equal. They are both exceptional
operating systems. Linux typically has more hardware support (more
hackers churning out drivers, more users for testing obscure stuff).
FreeBSD has (used to have, at least) a better VM system that scaled
with load more reliably than Linux.
As others will no doubt tell you, go with the one that will take the
least of YOUR time. Your computer won't care that much.
FreeBSD rules. Linux is for weenies. You decide which you want to
be known as.
Oh, and Linux, at the moment, has better SMP support (hey, this is
changing very quickly, though, for FreeBSD-current). So if you're
thinking of getting a multi-processor box, you might want to consider
that.
When you say, "they're not there, yet", do you mean that kernel
threads are not available in FreeBSD, or that they're not at a
level of stability/performance that you'd be comfortable with?
Because I can assure you that they're available, and with a
recent FreeBSD (3.2) the stability is excellent and the performance
is very good. I've been using kernel threads with FreeBSD since
early this year with not a single crash, lockup, or problem.
There are some performance issues when using FreeBSD's kernel
threads and SMP, because right now a large portion of the kernel
has to be locked. The developers are working on bringing the
locks further into the kernel, so that multiple processes can be
working in the kernel at the same time. But if you're using a
single-processor machine, FreeBSD kernel threads work very well.
There's no need to use MIT-pthreads on FreeBSD.
(Thimble Smith)
...
It may be worth mentioning that, from a purely subjective point of view
as someone who's watched this list for a long time, MySQL appears to be
better _supported_ on Linux.
My understanding is that TcX's main UNIX development environments are
Solaris and Linux, and I know that there have been problems with, e.g.,
FreeBSD thread support and MySQL.
(Paul D. Smith)
...
lets speak about network layers, since network is in the "performance
chain",
i was told network layers are tightly integrated to the FreeBSD kernel
although Linux network is a kernel extension.
could someone tell me is Linux network layer is multithreaded ?
this could be an issue for performance problems
the ultimate solution will be certainly : try both...as it is
transparent for Database clients
(Christian Bruno)
--
※ 修改:·golf 於 Nov 28 03:45:11 修改本文·[FROM: 210.74.148.187]
※ 来源:·BBS 荔园晨风站 bbs.szu.edu.cn·[FROM: 210.74.148.187]
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