From: Linus Torvalds <torvalds@linux-foundation.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Mark Hemment <markhemm@googlemail.com>,
Andrew Morton <akpm@linux-foundation.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
patrice.chotard@foss.st.com,
Mikulas Patocka <mpatocka@redhat.com>,
Lukas Czerner <lczerner@redhat.com>,
Christoph Hellwig <hch@lst.de>,
"Darrick J. Wong" <djwong@kernel.org>,
Chuck Lever <chuck.lever@oracle.com>,
Hugh Dickins <hughd@google.com>,
patches@lists.linux.dev, Linux-MM <linux-mm@kvack.org>,
mm-commits@vger.kernel.org
Subject: Re: [patch 02/14] tmpfs: fix regressions from wider use of ZERO_PAGE
Date: Thu, 21 Apr 2022 09:50:39 -0700 [thread overview]
Message-ID: <CAHk-=wgf2C9nFiC+3UFG4k7XVTQq5aV6fasSYuT_nQeo_Yew6A@mail.gmail.com> (raw)
In-Reply-To: <YmFy8DEqvX4FlnuB@zn.tnic>
[-- Attachment #1: Type: text/plain, Size: 1159 bytes --]
On Thu, Apr 21, 2022 at 8:06 AM Borislav Petkov <bp@alien8.de> wrote:
>
> on AMD zen3
>
> original: 20.11 Gb/s
> rep_good: 34.662 Gb/s
> erms: 36.378 Gb/s
> fsrm: 36.398 Gb/s
Looks good.
Of course, the interesting cases are the "took a page fault in the middle" ones.
A very simple basic test is something like the attached.
It does no error checking or anything else, but doing a 'strace
./a.out' should give you something like
...
openat(AT_FDCWD, "/dev/zero", O_RDONLY) = 3
mmap(NULL, 196608, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7f10ddfd0000
munmap(0x7f10ddfe0000, 65536) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 65536) = 16
exit_group(16) = ?
where that "read(..) = 16" is the important part. It correctly figured
out that it can only do 16 bytes (ok, 17, but we've always allowed the
user accessor functions to block).
With erms/fsrm, presumably you get that optimal "read(..) = 17".
I'm sure we have a test-case for this somewhere, but it was easier for
me to write a few lines of (bad) code than try to find it.
Linus
[-- Attachment #2: t.c --]
[-- Type: text/x-csrc, Size: 397 bytes --]
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
// Whatever
#define PAGE_SIZE 65536
int main(int argc, char **argv)
{
int fd;
void *map;
fd = open("/dev/zero", O_RDONLY);
map = mmap(NULL, 3*PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE |MAP_ANONYMOUS , -1, 0);
munmap(map + PAGE_SIZE, PAGE_SIZE);
return read(fd, map + PAGE_SIZE - 17, PAGE_SIZE);
}
next prev parent reply other threads:[~2022-04-21 16:51 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-15 2:12 incoming Andrew Morton
2022-04-15 2:13 ` [patch 01/14] MAINTAINERS: Broadcom internal lists aren't maintainers Andrew Morton
2022-04-15 2:13 ` [patch 02/14] tmpfs: fix regressions from wider use of ZERO_PAGE Andrew Morton
2022-04-15 22:10 ` Linus Torvalds
2022-04-15 22:21 ` Matthew Wilcox
2022-04-15 22:41 ` Hugh Dickins
2022-04-16 6:36 ` Borislav Petkov
2022-04-16 14:07 ` Mark Hemment
2022-04-16 17:28 ` Borislav Petkov
2022-04-16 17:42 ` Linus Torvalds
2022-04-16 21:15 ` Borislav Petkov
2022-04-17 19:41 ` Borislav Petkov
2022-04-17 20:56 ` Linus Torvalds
2022-04-18 10:15 ` Borislav Petkov
2022-04-18 17:10 ` Linus Torvalds
2022-04-19 9:17 ` Borislav Petkov
2022-04-19 16:41 ` Linus Torvalds
2022-04-19 17:48 ` Borislav Petkov
2022-04-21 15:06 ` Borislav Petkov
2022-04-21 16:50 ` Linus Torvalds [this message]
2022-04-21 17:22 ` Linus Torvalds
2022-04-24 19:37 ` Borislav Petkov
2022-04-24 19:54 ` Linus Torvalds
2022-04-24 20:24 ` Linus Torvalds
2022-04-27 0:14 ` Borislav Petkov
2022-04-27 1:29 ` Linus Torvalds
2022-04-27 10:41 ` Borislav Petkov
2022-04-27 16:00 ` Linus Torvalds
2022-05-04 18:56 ` Borislav Petkov
2022-05-04 19:22 ` Linus Torvalds
2022-05-04 20:18 ` Borislav Petkov
2022-05-04 20:40 ` Linus Torvalds
2022-05-04 21:01 ` Borislav Petkov
2022-05-04 21:09 ` Linus Torvalds
2022-05-10 9:31 ` clear_user (was: [patch 02/14] tmpfs: fix regressions from wider use of ZERO_PAGE) Borislav Petkov
2022-05-10 17:17 ` Linus Torvalds
2022-05-10 17:28 ` Linus Torvalds
2022-05-10 18:10 ` Borislav Petkov
2022-05-10 18:57 ` Borislav Petkov
2022-05-24 12:32 ` [PATCH] x86/clear_user: Make it faster Borislav Petkov
2022-05-24 16:51 ` Linus Torvalds
2022-05-24 17:30 ` Borislav Petkov
2022-05-25 12:11 ` Mark Hemment
2022-05-27 11:28 ` Borislav Petkov
2022-05-27 11:10 ` Ingo Molnar
2022-06-22 14:21 ` Borislav Petkov
2022-06-22 15:06 ` Linus Torvalds
2022-06-22 20:14 ` Borislav Petkov
2022-06-22 21:07 ` Linus Torvalds
2022-06-23 9:41 ` Borislav Petkov
2022-07-05 17:01 ` [PATCH -final] " Borislav Petkov
2022-07-06 9:24 ` Alexey Dobriyan
2022-07-11 10:33 ` Borislav Petkov
2022-07-12 12:32 ` Alexey Dobriyan
2022-08-06 12:49 ` Borislav Petkov
2022-04-15 2:13 ` [patch 03/14] mm/secretmem: fix panic when growing a memfd_secret Andrew Morton
2022-04-15 2:13 ` [patch 04/14] irq_work: use kasan_record_aux_stack_noalloc() record callstack Andrew Morton
2022-04-15 2:13 ` [patch 05/14] kasan: fix hw tags enablement when KUNIT tests are disabled Andrew Morton
2022-04-15 2:13 ` [patch 06/14] mm, kfence: support kmem_dump_obj() for KFENCE objects Andrew Morton
2022-04-15 2:13 ` [patch 07/14] mm, page_alloc: fix build_zonerefs_node() Andrew Morton
2022-04-15 2:13 ` [patch 08/14] mm: fix unexpected zeroed page mapping with zram swap Andrew Morton
2022-04-15 2:13 ` [patch 09/14] mm: compaction: fix compiler warning when CONFIG_COMPACTION=n Andrew Morton
2022-04-15 2:13 ` [patch 10/14] hugetlb: do not demote poisoned hugetlb pages Andrew Morton
2022-04-15 2:13 ` [patch 11/14] revert "fs/binfmt_elf: fix PT_LOAD p_align values for loaders" Andrew Morton
2022-04-15 2:13 ` [patch 12/14] revert "fs/binfmt_elf: use PT_LOAD p_align values for static PIE" Andrew Morton
2022-04-15 2:14 ` [patch 13/14] mm/vmalloc: fix spinning drain_vmap_work after reading from /proc/vmcore Andrew Morton
2022-04-15 2:14 ` [patch 14/14] mm: kmemleak: take a full lowmem check in kmemleak_*_phys() Andrew Morton
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