Messages in this thread | | | Date | Tue, 8 May 2001 14:23:56 -0300 (BRT) | From | Marcelo Tosatti <> | Subject | Re: [PATCH] allocation looping + kswapd CPU cycles |
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On Tue, 8 May 2001, Mark Hemment wrote:
> > In 2.4.3pre6, code in page_alloc.c:__alloc_pages(), changed from; > > try_to_free_pages(gfp_mask); > wakeup_bdflush(); > if (!order) > goto try_again; > to > try_to_free_pages(gfp_mask); > wakeup_bdflush(); > goto try_again; > > > This introduced the effect of a non-zero order, __GFP_WAIT allocation > (without PF_MEMALLOC set), never returning failure. The allocation keeps > looping in __alloc_pages(), kicking kswapd, until the allocation succeeds. > > If there is plenty of memory in the free-pools and inactive-lists > free_shortage() will return false, causing the state of these > free-pools/inactive-lists not to be 'improved' by kswapd. > > If there is nothing else changing/improving the free-pools or > inactive-lists, the allocation loops forever (kicking kswapd). > > Does anyone know why the 2.4.3pre6 change was made?
Because wakeup_bdflush(0) can wakeup bdflush _even_ if it does not have any job to do (ie less than 30% dirty buffers in the default config).
> > The attached patch (against 2.4.5-pre1) fixes the looping symptom, by > adding a counter and looping only twice for non-zero order allocations.
Looks good. (actually Rik had a patch similar to this which fixed a real case with cdda2wav just like you described)
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