Messages in this thread | | | Date | Wed, 12 Oct 2011 15:58:31 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH -v2 -mm] add extra free kbytes tunable |
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On 10/12/2011 03:20 PM, Andrew Morton wrote: > On Wed, 12 Oct 2011 09:09:17 -0400 > Rik van Riel<riel@redhat.com> wrote:
>> The problem is that we may be dealing with bursts, not steady >> states of allocations. Without knowing the size of a burst, >> we have no idea when we should wake up kswapd to get enough >> memory freed ahead of the application's allocations. > > That problem remains with this patch - it just takes a larger burst. > > Unless the admin somehow manages to configure the tunable large enough > to cover the largest burst, and there aren't other applications > allocating memory during that burst, and the time between bursts is > sufficient for kswapd to be able to sufficiently replenish free-page > reserves. All of which sounds rather unlikely.
It depends on the system. For a setup which is packed to the brim with workloads, this patch is not likely to help. On the other hand, on a system that is packed to the brim with workloads, you are unlikely to get low latencies anyway.
For situations where people really care about low latencies, I imagine having dedicated hardware for a workload is not at all unusual, and the patch works for that.
>>> Look, please don't go bending over backwards like this to defend a bad >>> patch. It's a bad patch! It would be better not to have to merge it. >>> Let's do something better. >> >> I would love it if we could come up with something better, >> and have thought about it a lot. >> >> However, so far we do not seem to have an alternative yet :( > > Do we actually have a real-world application which is hurting from > this?
Satoru-san?
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