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因为内核支持合并块操作, 所以通过ioblock.request触发的块请求, 可能被合并掉, 因此通过对函数kernel.trace("block_bio_frontmerge"),&kernel.trace("block_bio_backmerge")的事件跟踪, 可以得到块设备上精确的块操作统计情况.脚本内容以及注解 :&[root@db-172-16-3-150 network]# cd /usr/share/systemtap/testsuite/systemtap.examples/io[root@db-172-16-3-150 io]# cat ioblktime.stp#!/usr/bin/stapglobal req_time, etimes// req_time数组, 索引为上下文变量bio的内存地址. 值为当前时间// etimes数组, 索引为设备名, R|W字符串. 存储的值为ioblock的整个操作耗时的统计变量.// 如果数组元素超过默认的2048可能会导致运行错误退出, 那么可使用stap -D MAXMAPENTRIES=10240或者更大的值来规避这个错误,// 或者指定数组的长度global req_time[100000] 或者是使用rotate数组global req_time%[10000]probe ioblock.request{& req_time[$bio] = gettimeofday_us()}// 当ioblock请求发生时, 记录下内存地址和当前时间probe ioblock.end{& t = gettimeofday_us() &// 当前事件& s = &req_time[$bio] &// 根据bio找到ioblock.request事件记录的请求开始时间.& delete req_time[$bio] &// 删除请求开始时间& if (s) { &// 当请求未被合并时, 记录此次io操作的耗时.& & etimes[devname, bio_rw_str(rw)] &&& t - s& }}// 当io操作结束时, 记录下io操作耗时, 存放至统计数组./* for time being delete things that get merged with others */probe kernel.trace("block_bio_frontmerge"),& & & kernel.trace("block_bio_backmerge"){& delete req_time[$bio] &// 发生io合并时, 删除请求开始事件.}probe timer.s(10), end {& ansi_clear_screen() &// 清屏& printf("%10s %3s %10s %10s %10s\n",& & & & &"device", "rw", "total (us)", "count", "avg (us)") &// 输出头信息& foreach ([dev,rw] in etimes - limit 20) {& & printf("%10s %3s %10d %10d %10d\n", dev, rw,& & & & & &@sum(etimes[dev,rw]), @count(etimes[dev,rw]), @avg(etimes[dev,rw]))& }// 输出实际的io操作次数排名前20位的信息. 包含设备名, 读写, 总耗时, 实际io操作次数, 平均每次io的耗时.& delete etimes// 删除统计变量数组, 下10秒重新统计}执行输出举例 :&[root@db-172-16-3-150 io]# stap ioblktime.stp& & device &rw total (us) & & &count & avg (us)& & & &sdd & W & &5831844 & & & 2884 & & & 2022& & & sdd1 & W & & &12091 & & & 2868 & & & & &4& & & &sdb & W & & & 9210 & & & & &8 & & & 1151& & & sdb1 & W & & & &279 & & & & &6 & & & & 46& & & &sda & W & & &43526 & & & & &4 & & &10881& & & &sde & W & & & &580 & & & & &3 & & & &193本文用到的几个probe alias原型(包含对应的call原型).[root@db-172-16-3-150 io]# less /usr/share/systemtap/tapset/ioblock.stp/**&* &probe ioblock.request - Fires whenever making a generic block I/O request.&*&* &@name & & &- name of the probe point&* &@devname & - block device name&* &@ino & & & - i-node number of the mapped file&* &@sector & &- beginning sector for the entire bio&* &@flags & & - see below&* & & &BIO_UPTODATE & &0 & & & ok after I/O completion&* & & &BIO_RW_BLOCK & &1 & & & RW_AHEAD set, and read/write would block&* & & &BIO_EOF & & & & 2 & & & out-out-bounds error&* & & &BIO_SEG_VALID & 3 & & & nr_hw_seg valid&&* & & &BIO_CLONED & & &4 & & & doesn't own data&* & & &BIO_BOUNCED & & 5 & & & bio is a bounce bio&* & & &BIO_USER_MAPPED 6 & & & contains user pages&* & & &BIO_EOPNOTSUPP &7 & & & not supported&* &&* &@rw & & & &- binary trace for read/write request&* &@vcnt & & &- bio vector count which represents number of array element (page, offset, length) which make up this I/O request&* &@idx & & & - offset into the bio vector array&* &@phys_segments - number of segments in this bio after physical address coalescing is performed&* &@hw_segments - & number of segments after physical and DMA remapping hardware coalescing is performed&* &@size & & &- total size in bytes&* &@bdev & & &- target block device&* &@bdev_contains - points to the device object which contains the partition (when bio structure represents a partition)&* &@p_start_sect - &points to the start sector of the partition structure of the device&*&* Context:&* &The process makes block I/O request&*/probe ioblock.request = kernel.function ("generic_make_request"){& & & & name = "ioblock.request"& & & & devname = __bio_devname($bio)& & & & ino = __bio_ino($bio)& & & & sector = $bio-&bi_sector& & & & flags = $bio-&bi_flags& & & & rw = $bio-&bi_rw& & & & vcnt = $bio-&bi_vcnt& & & & idx = $bio-&bi_idx& & & & phys_segments = $bio-&bi_phys_segments& & & & hw_segments = (@defined($bio-&bi_hw_segments)& & & & & & & & & & & &? $bio-&bi_hw_segments : 0)& & & & size = $bio-&bi_size& & & & bdev = $bio-&bi_bdev& & & & bdev_contains = $bio-&bi_bdev-&bd_contains& & & & p_start_sect = __bio_start_sect($bio)}/**&* probe ioblock.end - Fires whenever a block I/O transfer is complete.&*&* &@name & & &- name of the probe point&* &@devname & - block device name&* &@ino & & & - i-node number of the mapped file&* &@bytes_done - number of bytes transferred&* &@sector & &- beginning sector for the entire bio&* &@flags & & - see below&* & & &BIO_UPTODATE & &0 & & & ok after I/O completion&* & & &BIO_RW_BLOCK & &1 & & & RW_AHEAD set, and read/write would block&* & & &BIO_EOF & & & & 2 & & & out-out-bounds error&* & & &BIO_SEG_VALID & 3 & & & nr_hw_seg valid&* & & &BIO_CLONED & & &4 & & & doesn't own data&* & & &BIO_BOUNCED & & 5 & & & bio is a bounce bio&* & & &BIO_USER_MAPPED 6 & & & contains user pages&* & & &BIO_EOPNOTSUPP &7 & & & not supported&* &@error & & - 0 on success&* &@rw & & & &- binary trace for read/write request&* &@vcnt & & &- bio vector count which represents number of array element (page, offset, length) which makes up this I/O request&* &@idx & & & - offset into the bio vector array&* &@phys_segments - number of segments in this bio after physical address coalescing is performed.&* &@hw_segments - & number of segments after physical and DMA remapping hardware coalescing is performed&* &@size & & &- total size in bytes&*&* Context:&* &The process signals the transfer is done.&*/probe ioblock.end = kernel.function("bio_endio"){& & & & name = "ioblock.end"& & & & devname = __bio_devname($bio)& & & & ino = __bio_ino($bio)& & & & bytes_done = (@defined($bytes_done) ? $bytes_done : $bio-&bi_size)& & & & error = $error& & & & sector = $bio-&bi_sector& & & & flags = $bio-&bi_flags& & & & rw = $bio-&bi_rw& & & & vcnt = $bio-&bi_vcnt& & & & idx = $bio-&bi_idx& & & & phys_segments = $bio-&bi_phys_segments& & & & hw_segments = (@defined($bio-&bi_hw_segments)& & & & & & & & & & & &? $bio-&bi_hw_segments : 0)& & & & size = $bio-&bi_size}// 把ioblock.end的rw变量转换成R,W字符串/* returns 0 for read, 1 for write */function bio_rw_num:long(rw:long)%{ /* pure */& & long rw = (long)STAP_ARG_& & STAP_RETVALUE = (rw & REQ_WRITE);%}/* returns R for read, W for write */function bio_rw_str(rw:long){& & return bio_rw_num(rw) == BIO_READ ? "R" : "W"}这几个函数的源码位置信息:&[root@db-172-16-3-150 io]# stap -L 'kernel.function ("generic_make_request")'kernel.function("generic_make_request@block/blk-core.c:1770") $bio:struct bio*[root@db-172-16-3-150 io]# stap -L 'kernel.function ("bio_endio")'kernel.function("bio_endio@fs/bio.c:1425") $bio:struct bio* $error:int[root@db-172-16-3-150 io]# stap -L 'kernel.trace("block_bio_backmerge")'kernel.trace("block_bio_backmerge") $q:struct request_queue* $bio:struct bio*[root@db-172-16-3-150 io]# stap -L 'kernel.trace("block_bio_frontmerge")'kernel.trace("block_bio_frontmerge") $q:struct request_queue* $bio:struct bio*源码 :&/usr/src/debug/kernel-2.6.32-358.el6/linux-2.6.32-358.el6.x86_64/block/blk-core.c/*&* We only want one -&make_request_fn to be active at a time,&* else stack usage with stacked devices could be a problem.&* So use current-&bio_{list,tail} to keep a list of requests&* submited by a make_request_fn function.&* current-&bio_tail is also used as a flag to say if&* generic_make_request is currently active in this task or not.&* If it is NULL, then no make_request is active. &If it is non-NULL,&* then a make_request is active, and new requests should be added&* at the tail&*/void generic_make_request(struct bio *bio){& & & & if (current-&bio_tail) {& & & & & & & & /* make_request is active */& & & & & & & & *(current-&bio_tail) =& & & & & & & & bio-&bi_next = NULL;& & & & & & & & current-&bio_tail = &bio-&bi_& & & & & & & && & & & }& & & & /* following loop may be a bit non-obvious, and so deserves some& & & & &* explanation.& & & & &* Before entering the loop, bio-&bi_next is NULL (as all callers& & & & &* ensure that) so we have a list with a single bio.& & & & &* We pretend that we have just taken it off a longer list, so& & & & &* we assign bio_list to the next (which is NULL) and bio_tail& & & & &* to &bio_list, thus initialising the bio_list of new bios to be& & & & &* added. &__generic_make_request may indeed add some more bios& & & & &* through a recursive call to generic_make_request. &If it& & & & &* did, we find a non-NULL value in bio_list and re-enter the loop& & & & &* from the top. &In this case we really did just take the bio& & & & &* of the top of the list (no pretending) and so fixup bio_list and& & & & &* bio_tail or bi_next, and call into __generic_make_request again.& & & & &*& & & & &* The loop was structured like this to make only one call to& & & & &* __generic_make_request (which is important as it is large and& & & & &* inlined) and to keep the structure simple.& & & & &*/& & & & BUG_ON(bio-&bi_next);& & & & do {& & & & & & & & current-&bio_list = bio-&bi_& & & & & & & & if (bio-&bi_next == NULL)& & & & & & & & & & & & current-&bio_tail = &current-&bio_& & & & & & & & else& & & & & & & & & & & & bio-&bi_next = NULL;& & & & & & & & __generic_make_request(bio);& & & & & & & & bio = current-&bio_& & & & } while (bio);& & & & current-&bio_tail = NULL; /* deactivate */}EXPORT_SYMBOL(generic_make_request);/usr/src/debug/kernel-2.6.32-358.el6/linux-2.6.32-358.el6.x86_64/fs/bio.c/**&* bio_endio - end I/O on a bio&* @bio: & & & &bio&* @error: & & &error, if any&*&* Description:&* & bio_endio() will end I/O on the whole bio. bio_endio() is the&* & preferred way to end I/O on a bio, it takes care of clearing&* & BIO_UPTODATE on error. @error is 0 on success, and and one of the&* & established -Exxxx (-EIO, for instance) error values in case&* & something went wrong. Noone should call bi_end_io() directly on a&* & bio unless they own it and thus know that it has an end_io&* & function.&**/void bio_endio(struct bio *bio, int error){& & & & if (error)& & & & & & & & clear_bit(BIO_UPTODATE, &bio-&bi_flags);& & & & else if (!test_bit(BIO_UPTODATE, &bio-&bi_flags))& & & & & & & & error = -EIO;& & & & if (bio-&bi_end_io)& & & & & & & & bio-&bi_end_io(bio, error);}EXPORT_SYMBOL(bio_endio);/usr/src/debug/kernel-2.6.32-358.el6/linux-2.6.32-358.el6.x86_64/include/trace/events/block.hDECLARE_EVENT_CLASS(block_bio,
TP_PROTO(struct request_queue *q, struct bio *bio),
TP_ARGS(q, bio),
TP_STRUCT__entry(
__field( dev_t,
__field( sector_t,
__field( unsigned int,
__array( char,
__array( char,
TASK_COMM_LEN
TP_fast_assign(
__entry-&dev
= bio-&bi_bdev-&bd_
__entry-&sector
= bio-&bi_
__entry-&nr_sector
= bio-&bi_size && 9;
blk_fill_rwbs(__entry-&rwbs, bio-&bi_rw, bio-&bi_size);
memcpy(__entry-&comm, current-&comm, TASK_COMM_LEN);
TP_printk("%d,%d %s %llu + %u [%s]",
MAJOR(__entry-&dev), MINOR(__entry-&dev), __entry-&rwbs,
(unsigned long long)__entry-&sector,
__entry-&nr_sector, __entry-&comm));DEFINE_EVENT(block_bio, block_bio_backmerge,& & & & TP_PROTO(struct request_queue *q, struct bio *bio),& & & & TP_ARGS(q, bio));DEFINE_EVENT(block_bio, block_bio_frontmerge,& & & & TP_PROTO(struct request_queue *q, struct bio *bio),& & & & TP_ARGS(q, bio));[参考]1.&2.&3. /usr/share/systemtap/testsuite/systemtap.examples4. systemtap-testsuite5. /usr/share/systemtap/testsuite/systemtap.examples/index.txt6. /usr/share/systemtap/testsuite/systemtap.examples/keyword-index.txt7. /usr/share/systemtap/tapset8.&
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blogTitle:'Systemtap examples, DISK IO - 7 Periodically Print I/O Block Time',
blogAbstract:'例子来自ioblktime.stp 脚本, 该脚本用以统计每个块设备的io块请求情况, 请求次数, io操作耗费的时间以systemtap的统计变量进程存储, 可以得到块设备上io块请求的平均时间, 总时间, 最大, 最小时间, 次数, 柱状图等等.因为内核支持合并块操作, 所以通过ioblock.request触发的块请求, 可能被合并掉, 因此通过对函数kernel.trace(\"block_bio_frontmerge\"),&kernel.trace(\"block_bio_backmerge\")的事件跟踪, 可以得到块设备上精确的块操作统计情况.脚本内容以及注解 :&[root@db-172-16-3-150',
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