On Sat 20-05-17 13:06:53, Pavel Tatashin wrote: [...] > /* > + * Adaptive scale is meant to reduce sizes of hash tables on large memory > + * machines. As memory size is increased the scale is also increased but at > + * slower pace. Starting from ADAPT_SCALE_BASE (64G), every time memory > + * quadruples the scale is increased by one, which means the size of hash table > + * only doubles, instead of quadrupling as well. > + */ > +#define ADAPT_SCALE_BASE (64ull << 30) I have only noticed this email today because my incoming emails stopped syncing since Friday. But this is _definitely_ not the right approachh. 64G for 32b systems is _way_ off. We have only ~1G for the kernel. I've already proposed scaling up to 32M for 32b systems and Andi seems to be suggesting the same. So can we fold or apply the following instead? --- >From 6a17a022e82ac715a08a9f4707c1c29a58a2225b Mon Sep 17 00:00:00 2001 From: Michal Hocko <mhocko@xxxxxxxx> Date: Mon, 22 May 2017 10:45:20 +0200 Subject: [PATCH] mm: fix adaptive hash table sizing for 32b systems Guenter Roeck has noticed that many qemu boot test on 32b systems and bisected it to "mm: drop HASH_ADAPT". The patch itself only makes the HASH_ADAPT unconditional for all users which shouldn't matter. Except it does because ADAPT_SCALE_BASE is 64GB which is out of 32b word size so the adapt_scale loop will never terminate and so HASH_EARLY allocations lock up with the patch while we even do not try to use the new hash adapt code because the early allocation suceeded. Fix this by reducint ADAPT_SCALE_BASE down to 32MB on 32b machines. Fixes: mm: adaptive hash table scaling Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> --- mm/page_alloc.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a26e19c3e1ff..70c5fc1fb89a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7174,11 +7174,15 @@ static unsigned long __init arch_reserved_kernel_pages(void) /* * Adaptive scale is meant to reduce sizes of hash tables on large memory * machines. As memory size is increased the scale is also increased but at - * slower pace. Starting from ADAPT_SCALE_BASE (64G), every time memory - * quadruples the scale is increased by one, which means the size of hash table - * only doubles, instead of quadrupling as well. + * slower pace. Starting from ADAPT_SCALE_BASE (64G on 64b systems and 32M + * on 32b), every time memory quadruples the scale is increased by one, which + * means the size of hash table only doubles, instead of quadrupling as well. */ +#if __BITS_PER_LONG == 64 #define ADAPT_SCALE_BASE (64ul << 30) +#else +#define ADAPT_SCALE_BASE (32ul << 20) +#endif #define ADAPT_SCALE_SHIFT 2 #define ADAPT_SCALE_NPAGES (ADAPT_SCALE_BASE >> PAGE_SHIFT) -- 2.11.0 -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
