On Mon, 2024-02-12 at 13:38 -0800, Suren Baghdasaryan wrote: > Memory allocation, v3 and final: > > Overview: > Low overhead [1] per-callsite memory allocation profiling. Not just for debug > kernels, overhead low enough to be deployed in production. > > We're aiming to get this in the next merge window, for 6.9. The feedback > we've gotten has been that even out of tree this patchset has already > been useful, and there's a significant amount of other work gated on the > code tagging functionality included in this patchset [2]. > > Example output: > root@moria-kvm:~# sort -h /proc/allocinfo|tail > 3.11MiB 2850 fs/ext4/super.c:1408 module:ext4 func:ext4_alloc_inode > 3.52MiB 225 kernel/fork.c:356 module:fork func:alloc_thread_stack_node > 3.75MiB 960 mm/page_ext.c:270 module:page_ext func:alloc_page_ext > 4.00MiB 2 mm/khugepaged.c:893 module:khugepaged func:hpage_collapse_alloc_folio > 10.5MiB 168 block/blk-mq.c:3421 module:blk_mq func:blk_mq_alloc_rqs > 14.0MiB 3594 include/linux/gfp.h:295 module:filemap func:folio_alloc_noprof > 26.8MiB 6856 include/linux/gfp.h:295 module:memory func:folio_alloc_noprof > 64.5MiB 98315 fs/xfs/xfs_rmap_item.c:147 module:xfs func:xfs_rui_init > 98.7MiB 25264 include/linux/gfp.h:295 module:readahead func:folio_alloc_noprof > 125MiB 7357 mm/slub.c:2201 module:slub func:alloc_slab_page > > Since v2: > - tglx noticed a circular header dependency between sched.h and percpu.h; > a bunch of header cleanups were merged into 6.8 to ameliorate this [3]. > > - a number of improvements, moving alloc_hooks() annotations to the > correct place for better tracking (mempool), and bugfixes. > > - looked at alternate hooking methods. > There were suggestions on alternate methods (compiler attribute, > trampolines), but they wouldn't have made the patchset any cleaner > (we still need to have different function versions for accounting vs. no > accounting to control at which point in a call chain the accounting > happens), and they would have added a dependency on toolchain > support. > > Usage: > kconfig options: > - CONFIG_MEM_ALLOC_PROFILING > - CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT > - CONFIG_MEM_ALLOC_PROFILING_DEBUG > adds warnings for allocations that weren't accounted because of a > missing annotation > > sysctl: > /proc/sys/vm/mem_profiling > > Runtime info: > /proc/allocinfo > > Notes: > > [1]: Overhead > To measure the overhead we are comparing the following configurations: > (1) Baseline with CONFIG_MEMCG_KMEM=n > (2) Disabled by default (CONFIG_MEM_ALLOC_PROFILING=y && > CONFIG_MEM_ALLOC_PROFILING_BY_DEFAULT=n) > (3) Enabled by default (CONFIG_MEM_ALLOC_PROFILING=y && > CONFIG_MEM_ALLOC_PROFILING_BY_DEFAULT=y) > (4) Enabled at runtime (CONFIG_MEM_ALLOC_PROFILING=y && > CONFIG_MEM_ALLOC_PROFILING_BY_DEFAULT=n && /proc/sys/vm/mem_profiling=1) > (5) Baseline with CONFIG_MEMCG_KMEM=y && allocating with __GFP_ACCOUNT > Thanks for the work on this patchset and it is quite useful. A clarification question on the data: I assume Config (2), (3) and (4) has CONFIG_MEMCG_KMEM=n, right? If so do you have similar data for config (2), (3) and (4) but with CONFIG_MEMCG_KMEM=y for comparison with (5)? Tim > Performance overhead: > To evaluate performance we implemented an in-kernel test executing > multiple get_free_page/free_page and kmalloc/kfree calls with allocation > sizes growing from 8 to 240 bytes with CPU frequency set to max and CPU > affinity set to a specific CPU to minimize the noise. Below are results > from running the test on Ubuntu 22.04.2 LTS with 6.8.0-rc1 kernel on > 56 core Intel Xeon: > > kmalloc pgalloc > (1 baseline) 6.764s 16.902s > (2 default disabled) 6.793s (+0.43%) 17.007s (+0.62%) > (3 default enabled) 7.197s (+6.40%) 23.666s (+40.02%) > (4 runtime enabled) 7.405s (+9.48%) 23.901s (+41.41%) > (5 memcg) 13.388s (+97.94%) 48.460s (+186.71%) >
