On Fri, Jun 24, 2016 at 12:45:49PM +0200, Peter Lieven wrote: > Am 24.06.2016 um 11:58 schrieb Peter Maydell: > > On 24 June 2016 at 10:37, Stefan Hajnoczi <stefa...@gmail.com> wrote: > >> On Wed, Jun 22, 2016 at 09:56:06PM +0100, Peter Maydell wrote: > >>> On 22 June 2016 at 20:55, Peter Lieven <p...@kamp.de> wrote: > >>>> What makes the coroutine pool memory intensive is the stack size of 1MB > >>>> per > >>>> coroutine. Is it really necessary to have such a big stack? > >>> That reminds me that I was wondering if we should allocate > >>> our coroutine stacks with MAP_GROWSDOWN (though if we're > >>> not actually using 1MB of stack then it's only going to > >>> be eating virtual memory, not necessarily real memory.) > >> Yes, MAP_GROWSDOWN will not reduce RSS. > > Right, but then the 1MB of stack as currently allocated isn't > > going to be affecting RSS either I would have thought (except > > transiently, since we zero it on allocation which will > > bring it into the RSS until it falls back out again > > because we don't touch it after that). > > What I observe regarding the coroutine pool is really strange. Under I/O load > while booting the vServer the RSS size is low as expected. If the vServer runs > for some time the RSS size suddenly explodes as if suddenly all the stack > memory gets > mapped. This symptom definetely goes away if I disable the pool. > > Regarding the coroutine pool I had the following thoughts: > - mmap the stack so its actually really freed if the coroutine is deleted > (with MAP_GROWSDOWN or not?)
This might be an easy fix if malloc is holding memory and not reusing it. Stefan
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