Linux
Apache strace 尋找記憶體洩漏
我們有一個存在記憶體問題的伺服器：伺服器一直為自己分配記憶體並且不釋放它。我們正在執行 Apache。我將 MaxReqsPerClient 設置為一個非常低的值，這樣執行緒就不會佔用很多記憶體，但是有人見過這樣的呼叫嗎？我認為這可能是 Drupal 從數據庫中的記憶體中拉回了太多數據，我錯了嗎？
read(52, "h_index\";a:2:{s:6:\"weight\";i:1;s"..., 6171) = 1368 read(52, "\";a:2:{s:6:\"author\";a:3:{s:5:\"la"..., 4803) = 1368 read(52, ":\"description\";s:19:\"Term name t"..., 3435) = 1368 read(52, "abel\";s:4:\"Name\";s:11:\"descripti"..., 2067) = 1368 read(52, "ions\";a:2:{s:4:\"form\";a:3:{s:4:\""..., 16384) = 708 brk(0x2ab554396000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55f653000 brk(0x2ab554356000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55f753000 brk(0x2ab554356000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55f853000 brk(0x2ab554356000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55f953000 brk(0x2ab554356000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55fa53000 brk(0x2ab554356000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55fb53000 brk(0x2ab554356000) = 0x2ab5542f5000 mmap(NULL, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ab55fc53000 poll([{fd=52, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout) write(52, "d\0\0\0\3SELECT cid, data, created, "..., 104) = 104 read(52, "\1\0\0\1\5E\0\0\2\3def\23drupal_database_nam"..., 16384) = 1368 read(52, ";s:11:\"granularity\";a:5:{s:4:\"ye"..., 34783) = 1368 read(52, ":4:\"date\";}s:9:\"datestamp\";a:9:{"..., 33415) = 1368 read(52, "\";i:0;s:15:\"display_default\";i:0"..., 32047) = 1368 read(52, "e as an integer value.\";s:8:\"set"..., 30679) = 1368 read(52, "label' pairs, i.e. 'Fraction': 0"..., 29311) = 1368頂部（procs 只是在記憶體中不斷增長..）：
12845 apache 15 0 581m 246m 37m S 0.0 4.1 0:17.39 httpd 12846 apache 15 0 571m 235m 37m S 0.0 4.0 0:12.13 httpd 12833 apache 15 0 420m 117m 37m S 0.0 2.0 0:06.04 httpd 12851 apache 15 0 412m 113m 37m S 0.0 1.9 0:05.32 httpd 13871 apache 15 0 409m 109m 37m S 0.0 1.8 0:04.90 httpd 12844 apache 15 0 407m 108m 37m S 0.0 1.8 0:04.50 httpd 13870 apache 15 0 407m 108m 37m S 0.3 1.8 0:03.50 httpd 14903 apache 15 0 402m 103m 37m S 0.3 1.7 0:01.29 httpd 14850 apache 15 0 397m 100m 37m S 0.0 1.7 0:02.08 httpd 14907 apache 15 0 390m 93m 36m S 0.0 1.6 0:01.32 httpd 13872 apache 15 0 386m 91m 37m S 0.0 1.5 0:03.13 httpd 12843 apache 15 0 373m 81m 37m S 0.0 1.4 0:02.51 httpd 14901 apache 15 0 370m 75m 33m S 0.0 1.3 0:00.78 httpd 14904 apache 15 0 335m 29m 15m S 0.0 0.5 0:00.26 httpd
我最終只是降低了 httpd.conf 中的 MaxRequestsPerChild，所以我的執行緒在它們變得太大之前就過期了。他們之前達到了 800M 並且有一些嚴重的交換，現在他們在死亡之前最多達到 250M。
這是在什麼時間段內發生的？記憶體使用量有多大？
如果時間足夠短，或者您暫時沒有在前台執行 Apache，您可以使用valgrind來查找記憶體洩漏…（可通過 YUM 獲得）
就像是：
valgrind --leak-check=full /usr/sbin/httpd輸出可能會顯示如下內容：
==945== LEAK SUMMARY: ==945== definitely lost: 15,595 bytes in 120 blocks ==945== indirectly lost: 1,917,248 bytes in 1,242 blocks ==945== possibly lost: 0 bytes in 0 blocks ==945== still reachable: 11,743 bytes in 89 blocks ==945== suppressed: 0 bytes in 0 blocks ==945== Reachable blocks (those to which a pointer was found) are not shown. ==945== To see them, rerun with: --leak-check=full --show-reachable=yes對於 Apache，我會看一下 PID。使用以下命令獲取 PID 值：
cat /var/run/httpd.pid或執行：pmap -x $(cat /var/run/httpd.pid)但在我有限的 Apache 經驗中，洩漏似乎總是與模組和腳本語言相關聯。也可能是記憶體…