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SubjectRe: [NET]: rt_check_expire() can take a long time, add a cond_resched()
On Thu, 15 Nov 2007 04:01:48 GMT
Linux Kernel Mailing List <linux-kernel@vger.kernel.org> wrote:

> Gitweb:
> http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d90bf5a976793edfa88d3bb2393f0231eb8ce1e5
> Commit: d90bf5a976793edfa88d3bb2393f0231eb8ce1e5 Parent:
> 66ba886254edbbd9442d30f1eef6f6fb0145027d Author: Eric Dumazet
> <dada1@cosmosbay.com> AuthorDate: Wed Nov 14 16:14:05 2007 -0800
> Committer: David S. Miller <davem@davemloft.net>
> CommitDate: Wed Nov 14 16:14:05 2007 -0800
>
> [NET]: rt_check_expire() can take a long time, add a
> cond_resched()
> On commit 39c90ece7565f5c47110c2fa77409d7a9478bd5b:

> When the IP route cache is big, rt_check_expire() can take a long
> time to run. (default settings : 20% of the hash table is scanned at
> each invocation)
>
> Adding cond_resched() helps giving cpu to higher priority tasks if
> necessary.
>
> Using a "if (need_resched())" test before calling
> "cond_resched();" is necessary to avoid spending too much time doing
> the resched check.

int __sched cond_resched(void)
{
if (need_resched() && .....

somehow I wonder why the second if() is useful at all; it's another
spot for a branch predictor to miss... and a void function call is
really really cheap...


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