On 16. 01. 24, 12:53, Jiri Slaby wrote:
Hi,
On 09. 08. 22, 20:24, Rik van Riel wrote:
Align larger anonymous memory mappings on THP boundaries by
going through thp_get_unmapped_area if THPs are enabled for
the current process.
With this patch, larger anonymous mappings are now THP aligned.
When a malloc library allocates a 2MB or larger arena, that
arena can now be mapped with THPs right from the start, which
can result in better TLB hit rates and execution time.
This appears to break 32bit processes on x86_64 (at least). In
particular, 32bit kernel or firefox builds in our build system.
Reverting this on top of 6.7 makes it work again.
Downstream report:
https://bugzilla.suse.com/show_bug.cgi?id=1218841
So running:
pahole -J --btf_gen_floats -j --lang_exclude=rust
--skip_encoding_btf_inconsistent_proto --btf_gen_optimized .tmp_vmlinux.btf
crashes or errors out with some random errors:
[182671] STRUCT idr's field 'idr_next' offset=128 bit_size=0 type=181346
Error emitting field
strace shows mmap() fails with ENOMEM right before the errors:
1223 mmap2(NULL, 5783552, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 <unfinished ...>
...
1223 <... mmap2 resumed>) = -1 ENOMEM (Cannot allocate
memory)
Note the .tmp_vmlinux.btf above can be arbitrary, but likely large
enough. For reference, one is available at:
https://decibel.fi.muni.cz/~xslaby/n/btf
Any ideas?
This works around the problem, of course (but is a band-aid, not a fix):
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1829,7 +1829,7 @@ get_unmapped_area(struct file *file, unsigned long
addr, unsigned long len,
*/
pgoff = 0;
get_area = shmem_get_unmapped_area;
- } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+ } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
!in_32bit_syscall()) {
/* Ensures that larger anonymous mappings are THP
aligned. */
get_area = thp_get_unmapped_area;
}
thp_get_unmapped_area() does not take care of the legacy stuff...
regards,
--
js
suse labs
