From: Robert Foss <robert.foss@xxxxxxxxxxxxx> This series provides the /proc/PID/totmaps feature, which summarizes the information provided by /proc/PID/smaps for improved performance and usability reasons. A use case is to speed up monitoring of memory consumption in environments where RSS isn't precise. For example Chrome tends to many processes which have hundreds of VMAs with a substantial amount of shared memory, and the error of using RSS rather than PSS tends to be very large when looking at overall memory consumption. PSS isn't kept as a single number that's exported like RSS, so to calculate PSS means having to parse a very large smaps file. This process is slow and has to be repeated for many processes, and we found that the just act of doing the parsing was taking up a significant amount of CPU time, so this patch is an attempt to make that process cheaper. /proc/PID/totmaps provides roughly a 2x speedup compared to parsing /proc/PID/smaps with awk. $ ps aux | grep firefox robertfoss 5025 24.3 13.7 3562820 2219616 ? Rl Aug15 277:44 /usr/lib/firefox/firefox https://allg.one/xpb $ awk '/^[0-9a-f]/{print}' /proc/5025/smaps | wc -l 1503 $ /usr/bin/time -v -p zsh -c "(repeat 25 {cat /proc/5025/totmaps})" [...] Command being timed: "zsh -c (repeat 25 {cat /proc/5025/totmaps})" User time (seconds): 0.00 System time (seconds): 0.40 Percent of CPU this job got: 90% Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.45 $ /usr/bin/time -v -p zsh -c "repeat 25 { awk '/^Rss/{rss+=\$2} /^Pss/{pss+=\$2} END {printf \"rss:%d pss:%d\n\", rss, pss}\' /proc/5025/smaps }" [...] Command being timed: "zsh -c repeat 25 { awk '/^Rss/{rss+=$2} /^Pss/{pss+=$2} END {printf "rss:%d pss:%d\n", rss, pss}\' /proc/5025/smaps }" User time (seconds): 0.37 System time (seconds): 0.45 Percent of CPU this job got: 92% Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.89 Changes since v1: - Removed IS_ERR check from get_task_mm() function - Changed comment format - Moved proc_totmaps_operations declaration inside internal.h - Switched to using do_maps_open() in totmaps_open() function, which provides privilege checking - Error handling reworked for totmaps_open() function - Switched to stack allocated struct mem_size_stats mss_sum in totmaps_proc_show() function - Removed get_task_mm() in totmaps_proc_show() since priv->mm already is available - Added support to proc_map_release() fork priv==NULL, to allow function to be used for all failure cases - Added proc_totmaps_op and for it helper functions - Added documention in separate patch - Removed totmaps_release() since it was just a wrapper for proc_map_release() Changes since v2: - Removed struct mem_size_stats *mss from struct proc_maps_private - Removed priv->task assignment in totmaps_open() call - Moved some assignements calls totmaps_open() around to increase code clarity - Moved some function calls to unlock data structures before printing Changes since v3: - Fixed typo in totmaps documentation - Fixed issue where proc_map_release wasn't called on error - Fixed put_task_struct not being called during .release() Changes since v4: - Prevent access to invalid processes Robert Foss (3): mm, proc: Implement /proc/<pid>/totmaps Documentation/filesystems: Fixed typo Documentation/filesystems: Added /proc/PID/totmaps documentation Documentation/filesystems/proc.txt | 23 +++++- fs/proc/base.c | 1 + fs/proc/internal.h | 2 + fs/proc/task_mmu.c | 148 +++++++++++++++++++++++++++++++++++++ 4 files changed, 173 insertions(+), 1 deletion(-) -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
