On Wed, 8 Mar 2000, Alan Cox wrote:
|> something simple and easily fixable. Linux kernel is not multithreaded and this
|> mean that when kernel doing work (say flushing MySQL data on disk) userlevel
|> process can not interrupt it. Work is going to improve situation (important
|
|Thats not correct. When disk I/O is being queued other userspace tasks run
|whenever the I/O blocks. So mysql will generate a lot of I/O and spend most
|of its time asleep where other stuff can run. Of course all the other stuff
|probably wants the disk too.
|
|At that point with heavy I/O the SMP scaling issues you mention kick in on
|2.2 as does the elevator algorithm flaw where we are starving some processes
|excessively under high I/O load.
If I remember properly, MySQL does not use mmaped files yet; if it would,
would that make a difference? Currently it may just be busy copying
buffers (I don't know how much of it is a userland issue vs. kernel
space).
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This archive was generated by hypermail 2b29 : Wed Mar 15 2000 - 21:00:14 EST