Messages in this thread | ![/](/images/icornerl.gif) | | From | Con Kolivas <> | Subject | Re: SMP performance problem in 2.4 (was: Athlon spinlock performance) | Date | Sun, 3 Aug 2003 15:18:45 +1000 |
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Hi Scott
On Sun, 3 Aug 2003 06:03, Scott L. Burson wrote: > In one approximately 60-second period with the problematic workload > running, `try_to_free_pages' was called 511 times. It made 2597 calls to > `shrink_caches', which made 2592 calls to `shrink_cache' (i.e. it was very > rare for `kmem_cache_reap' to release enough pages itself). The main loop > of `shrink_cache' was executed -- brace yourselves -- 189 million times! > During that time it called `page_cache_release' on only 31265 pages.
I noticed a curly section of the vm code when I was playing around with some hacks that are in the -ck kernel and this section might be helpful as it wasn't a hack so much as a fix in mm/vmscan.c around line 600. The problem is when the priority drops to 1 it should do the most cache reaping but instead bypasses some of it. You could try this modification and see if it helps.
This isn't a real patch but you should get the idea.
Con
nr_pages -= kmem_cache_reap(gfp_mask); - if (nr_pages <= 0) - return 0; + if (nr_pages < 1) + goto shrinkcheck;
nr_pages = chunk_size; /* try to keep the active list 2/3 of the size of the cache */ ratio = (unsigned long) nr_pages * nr_active_pages / ((nr_inactive_pages + 1) * 2); refill_inactive(ratio); nr_pages = shrink_cache(nr_pages, classzone, gfp_mask, priority); - if (nr_pages <= 0) - return 0; + /* + * Will return if nr_pages have been freed unless the + * priority managed to reach 1. If the vm is under this much + * pressure then shrink the d/i/dqcaches regardless. CK 2003 + */ +shrinkcheck: + if (nr_pages < 1){ + if (priority > 1) + return 0; + else + nr_pages = 0; + } +
shrink_dcache_memory(priority, gfp_mask); shrink_icache_memory(priority, gfp_mask);
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