Messages in this thread | | | Date | Fri, 18 Jul 2014 17:23:12 +0900 | From | Gioh Kim <> | Subject | Re: [PATCH] CMA/HOTPLUG: clear buffer-head lru before page migration |
| |
2014-07-18 오후 4:50, Marek Szyprowski 쓴 글: > Hello, > > On 2014-07-18 08:45, Gioh Kim wrote: >> For page migration of CMA, buffer-heads of lru should be dropped. >> Please refer to https://lkml.org/lkml/2014/7/4/101 for the history. >> >> I have two solution to drop bhs. >> One is invalidating entire lru. >> Another is searching the lru and dropping only one bh that Laura proposed >> at https://lkml.org/lkml/2012/8/31/313. >> >> I'm not sure which has better performance. >> So I did performance test on my cortex-a7 platform with Lmbench >> that has "File & VM system latencies" test. >> I am attaching the results. >> The first line is of invalidating entire lru and the second is dropping selected bh. >> >> File & VM system latencies in microseconds - smaller is better >> ------------------------------------------------------------------------------- >> Host OS 0K File 10K File Mmap Prot Page 100fd >> Create Delete Create Delete Latency Fault Fault selct >> --------- ------------- ------ ------ ------ ------ ------- ----- ------- ----- >> 10.178.33 Linux 3.10.19 25.1 19.6 32.6 19.7 5098.0 0.666 3.45880 6.506 >> 10.178.33 Linux 3.10.19 24.9 19.5 32.3 19.4 5059.0 0.563 3.46380 6.521 >> >> >> I tried several times but the result tells that they are the same under 1% gap >> except Protection Fault. >> But the latency of Protection Fault is very small and I think it has little effect. >> >> Therefore we can choose anything but I choose invalidating entire lru. >> The try_to_free_buffers() which is calling drop_buffers() is called by many filesystem code. >> So I think inserting codes in drop_buffers() can affect the system. >> And also we cannot distinguish migration type in drop_buffers(). >> >> In alloc_contig_range() we can distinguish migration type and invalidate lru if it needs. >> I think alloc_contig_range() is proper to deal with bh like following patch. >> >> Laura, can I have you name on Acked-by line? >> Please let me represent my thanks. >> >> Thanks for any feedback. >> >> ------------------------------- 8< ---------------------------------- >> >> >From 33c894b1bab9bc26486716f0c62c452d3a04d35d Mon Sep 17 00:00:00 2001 >> From: Gioh Kim <gioh.kim@lge.com> >> Date: Fri, 18 Jul 2014 13:40:01 +0900 >> Subject: [PATCH] CMA/HOTPLUG: clear buffer-head lru before page migration >> >> The bh must be free to migrate a page at which bh is mapped. >> The reference count of bh is increased when it is installed >> into lru so that the bh of lru must be freed before migrating the page. >> >> This frees every bh of lru. We could free only bh of migrating page. >> But searching lru costs more than invalidating entire lru. >> >> Signed-off-by: Gioh Kim <gioh.kim@lge.com> >> Acked-by: Laura Abbott <lauraa@codeaurora.org> >> --- >> mm/page_alloc.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index b99643d4..3b474e0 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6369,6 +6369,9 @@ int alloc_contig_range(unsigned long start, unsigned long end, >> if (ret) >> return ret; >> >> + if (migratetype == MIGRATE_CMA || migratetype == MIGRATE_MOVABLE) > > I'm not sure if it really makes sense to check the migratetype here. This check > doesn't add any new information to the code and make false impression that this > function can be called for other migratetypes than CMA or MOVABLE. Even if so, > then invalidating bh_lrus unconditionally will make more sense, IMHO.
I agree. I cannot understand why alloc_contig_range has an argument of migratetype. Can the alloc_contig_range is called for other migrate type than CMA/MOVABLE?
What do you think about removing the argument of migratetype and checking migratetype (if (migratetype == MIGRATE_CMA || migratetype == MIGRATE_MOVABLE))?
> >> + invalidate_bh_lrus(); >> + >> ret = __alloc_contig_migrate_range(&cc, start, end); >> if (ret) >> goto done; >> -- >> 1.7.9.5 >> > > Best regards -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |