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e34cbd3074
We can hook this up to the block layer, to help throttle buffered
writes.
wbt registers a few trace points that can be used to track what is
happening in the system:
wbt_lat: 259:0: latency 2446318
wbt_stat: 259:0: rmean=2446318, rmin=2446318, rmax=2446318, rsamples=1,
wmean=518866, wmin=15522, wmax=5330353, wsamples=57
wbt_step: 259:0: step down: step=1, window=72727272, background=8, normal=16, max=32
This shows a sync issue event (wbt_lat) that exceeded it's time. wbt_stat
dumps the current read/write stats for that window, and wbt_step shows a
step down event where we now scale back writes. Each trace includes the
device, 259:0 in this case.
Signed-off-by: Jens Axboe <axboe@fb.com>
154 lines
3.7 KiB
C
154 lines
3.7 KiB
C
#undef TRACE_SYSTEM
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#define TRACE_SYSTEM wbt
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#if !defined(_TRACE_WBT_H) || defined(TRACE_HEADER_MULTI_READ)
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#define _TRACE_WBT_H
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#include <linux/tracepoint.h>
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#include "../../../block/blk-wbt.h"
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/**
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* wbt_stat - trace stats for blk_wb
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* @stat: array of read/write stats
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*/
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TRACE_EVENT(wbt_stat,
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TP_PROTO(struct backing_dev_info *bdi, struct blk_rq_stat *stat),
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TP_ARGS(bdi, stat),
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TP_STRUCT__entry(
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__array(char, name, 32)
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__field(s64, rmean)
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__field(u64, rmin)
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__field(u64, rmax)
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__field(s64, rnr_samples)
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__field(s64, rtime)
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__field(s64, wmean)
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__field(u64, wmin)
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__field(u64, wmax)
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__field(s64, wnr_samples)
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__field(s64, wtime)
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),
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TP_fast_assign(
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strncpy(__entry->name, dev_name(bdi->dev), 32);
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__entry->rmean = stat[0].mean;
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__entry->rmin = stat[0].min;
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__entry->rmax = stat[0].max;
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__entry->rnr_samples = stat[0].nr_samples;
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__entry->wmean = stat[1].mean;
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__entry->wmin = stat[1].min;
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__entry->wmax = stat[1].max;
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__entry->wnr_samples = stat[1].nr_samples;
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),
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TP_printk("%s: rmean=%llu, rmin=%llu, rmax=%llu, rsamples=%llu, "
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"wmean=%llu, wmin=%llu, wmax=%llu, wsamples=%llu\n",
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__entry->name, __entry->rmean, __entry->rmin, __entry->rmax,
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__entry->rnr_samples, __entry->wmean, __entry->wmin,
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__entry->wmax, __entry->wnr_samples)
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);
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/**
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* wbt_lat - trace latency event
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* @lat: latency trigger
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*/
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TRACE_EVENT(wbt_lat,
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TP_PROTO(struct backing_dev_info *bdi, unsigned long lat),
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TP_ARGS(bdi, lat),
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TP_STRUCT__entry(
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__array(char, name, 32)
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__field(unsigned long, lat)
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),
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TP_fast_assign(
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strncpy(__entry->name, dev_name(bdi->dev), 32);
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__entry->lat = div_u64(lat, 1000);
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),
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TP_printk("%s: latency %lluus\n", __entry->name,
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(unsigned long long) __entry->lat)
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);
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/**
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* wbt_step - trace wb event step
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* @msg: context message
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* @step: the current scale step count
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* @window: the current monitoring window
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* @bg: the current background queue limit
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* @normal: the current normal writeback limit
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* @max: the current max throughput writeback limit
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*/
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TRACE_EVENT(wbt_step,
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TP_PROTO(struct backing_dev_info *bdi, const char *msg,
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int step, unsigned long window, unsigned int bg,
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unsigned int normal, unsigned int max),
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TP_ARGS(bdi, msg, step, window, bg, normal, max),
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TP_STRUCT__entry(
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__array(char, name, 32)
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__field(const char *, msg)
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__field(int, step)
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__field(unsigned long, window)
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__field(unsigned int, bg)
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__field(unsigned int, normal)
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__field(unsigned int, max)
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),
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TP_fast_assign(
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strncpy(__entry->name, dev_name(bdi->dev), 32);
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__entry->msg = msg;
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__entry->step = step;
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__entry->window = div_u64(window, 1000);
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__entry->bg = bg;
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__entry->normal = normal;
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__entry->max = max;
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),
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TP_printk("%s: %s: step=%d, window=%luus, background=%u, normal=%u, max=%u\n",
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__entry->name, __entry->msg, __entry->step, __entry->window,
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__entry->bg, __entry->normal, __entry->max)
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);
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/**
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* wbt_timer - trace wb timer event
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* @status: timer state status
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* @step: the current scale step count
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* @inflight: tracked writes inflight
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*/
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TRACE_EVENT(wbt_timer,
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TP_PROTO(struct backing_dev_info *bdi, unsigned int status,
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int step, unsigned int inflight),
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TP_ARGS(bdi, status, step, inflight),
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TP_STRUCT__entry(
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__array(char, name, 32)
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__field(unsigned int, status)
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__field(int, step)
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__field(unsigned int, inflight)
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),
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TP_fast_assign(
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strncpy(__entry->name, dev_name(bdi->dev), 32);
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__entry->status = status;
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__entry->step = step;
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__entry->inflight = inflight;
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),
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TP_printk("%s: status=%u, step=%d, inflight=%u\n", __entry->name,
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__entry->status, __entry->step, __entry->inflight)
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);
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#endif /* _TRACE_WBT_H */
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/* This part must be outside protection */
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#include <trace/define_trace.h>
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