Package: linux-image-amd64 Version: 5.4.13-1~bpo10+1 Severity: important Tags: upstream patch
Dear Maintainer, A performance regression stemming from the patch "mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()" in all mainline and current stable kernels, except 3.16.y, was reported by multiple persons [1]. The regression involves any activity that exercises vmalloc a lot, such as creating threads with CONFIG_VMAP_STACK=y or tty allocation (for example by SSH servers). A fix [2] for this was posted last October and was picked up in the -mm tree last November [3]. However this fix did not make it into v5.6-rc or any other release. It is still only in the -mm tree. AFAICT this regression only impacts x86 platforms, as it is the only platform that has a custom vmalloc_sync_all() instead of the standard no-op stub. As per my report to upstream, I currently have one production server running with the offending patch reverted. I also have another with the fix applied, and that seems to work well. Please consider adding the fix to Debian kernel images until upstream kernels have it. [1] https://www.spinics.net/lists/stable/msg349763.html [2] https://patchwork.kernel.org/patch/11181159/ [3] https://www.spinics.net/lists/mm-commits/msg141749.html -- System Information: Debian Release: 10.3 APT prefers stable-updates APT policy: (500, 'stable-updates'), (500, 'stable') Architecture: amd64 (x86_64) Foreign Architectures: armhf, i386, arm64 Kernel: Linux 5.2.0-0.bpo.2-amd64 (SMP w/8 CPU cores) Locale: LANG=zh_TW.UTF-8, LC_CTYPE=zh_TW.UTF-8 (charmap=UTF-8), LANGUAGE=zh_TW.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: sysvinit (via /sbin/init) Versions of packages linux-image-amd64 depends on: ii linux-image-5.4.0-0.bpo.3-amd64 5.4.13-1~bpo10+1 linux-image-amd64 recommends no packages. linux-image-amd64 suggests no packages. -- no debconf information
