Messages in this thread | | | Date | Fri, 29 Jul 2022 20:46:29 +0100 | From | Matthew Wilcox <> | Subject | Re: [PATCH] x86/sys_x86_64: fix VMA alginment for mmap file to THP |
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On Fri, Jul 29, 2022 at 12:42:14PM -0700, alexlzhu@devvm6390.atn0.facebook.com wrote: > From: alexlzhu <alexlzhu@fb.com> > > With CONFIG_READ_ONLY_THP_FOR_FS, the Linux kernel supports using THPs for > read-only mmapped files, such as shared libraries. However, on x86 the > kernel makes no attempt to actually align those mappings on 2MB boundaries, > which makes it impossible to use those THPs most of the time. This issue > applies to general file mapping THP as well as existing setups using > CONFIG_READ_ONLY_THP_FOR_FS. This is easily fixed by using the alignment > info passed to vm_unmapped_area. The problem can be seen in > /proc/PID/smaps where THPeligible is set to 0 on mappings to eligible > shared object files as shown below.
Can't your filesystem just use thp_get_unmapped_area() like ext2/ext4/fuse/xfs do?
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