Messages in this thread | | | Date | Wed, 04 Apr 2007 07:41:31 +0200 | From | Eric Dumazet <> | Subject | Re: missing madvise functionality |
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Nick Piggin a écrit : > Eric Dumazet wrote: >> >> I do think such workloads might benefit from a vma_cache not shared by >> all threads but private to each thread. A sequence could invalidate >> the cache(s). >> >> ie instead of a mm->mmap_cache, having a mm->sequence, and each thread >> having a current->mmap_cache and current->mm_sequence > > I have a patchset to do exactly this, btw.
Could you repost it please ?
I guess a seqlock could avoid some cache line bouncing on mmap_sem for some kind of operations. I wonder if it could speed up do_page_fault() ???
> > Anyway what is the status of the private futex work. I don't think that > is very intrusive or complicated, so it should get merged ASAP (so then > at least we have the interface there). >
It seems nobody but you and me cared.
BTW I am surprised of Ulrich bugging linux on MADV_KERNEL_CAN_DROP, while glibc still does :
FILE *F = fopen("/etc/passwd", "r"); fget(line, sizeof(line), F); fclose(F);
->
open("/etc/passwd", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=1505, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2b67097f0000 read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1505 close(3) = 0 munmap(0x2b67097f0000, 4096) = 0
using mmap()/munmap() to allocate one 4096 bytes area is certainly overkill. mmap_sem is apparently the thing we must hit forever.
Maybe nobody but me still uses fopen()/fclose() after all ?
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