On Fri, 16 Sep 2016 04:33:36 -0400
Pradeep Jagadeesh <pradeepkiruv...@gmail.com> wrote:

> Uses throttling APIs to limit I/O bandwidth and number of operations on the 
> fsdev devices.
> 
> Signed-off-by: Pradeep Jagadeesh <pradeep.jagade...@huawei.com>
> ---

Hi Pradeep,

Please find some comments below.

>  fsdev/Makefile.objs         |   1 +
>  fsdev/file-op-9p.h          |   3 +
>  fsdev/qemu-fsdev-opts.c     |  76 ++++++++++++++++++
>  fsdev/qemu-fsdev-throttle.c | 191 
> ++++++++++++++++++++++++++++++++++++++++++++
>  fsdev/qemu-fsdev-throttle.h |  42 ++++++++++

Is the qemu- prefix really needed ?

>  hw/9pfs/9p-local.c          |  11 ++-
>  hw/9pfs/9p.c                |   7 ++
>  hw/9pfs/cofile.c            |   3 +
>  8 files changed, 332 insertions(+), 2 deletions(-)
>  create mode 100644 fsdev/qemu-fsdev-throttle.c
>  create mode 100644 fsdev/qemu-fsdev-throttle.h
> 
> This adds the support for the 9p-local driver.
> For now this functionality can be enabled only through qemu cli options.
> QMP interface and support to other drivers need further extensions.
> To make it simple for other drivers, the throttle code has been put in
> separate files.
> 
> v1 -> v2:
> 
> -Fixed FsContext redeclaration issue
> -Removed couple of function declarations from 9p-throttle.h
> -Fixed some of the .help messages
> 
> v2 -> v3:
> 
> -Addressed follwing comments by Claudio Fontana
>  -Removed redundant memset calls in fsdev_throttle_configure_iolimits function
>  -Checking throttle structure validity before initializing other structures
>   in fsdev_throttle_configure_iolimits
> 
> -Addressed following comments by Greg Kurz
>  -Moved the code from 9pfs directory to fsdev directory, because the 
> throttling
>   is for the fsdev devices.Renamed the files and functions to fsdev_ from 
> 9pfs_
>  -Renamed throttling cli options to throttling.*, as in QMP cli options
>  -Removed some of the unwanted .h files from qemu-fsdev-throttle.[ch]
>  -Using throttle_enabled() function to set the thottle enabled flag for fsdev.
> 
> diff --git a/fsdev/Makefile.objs b/fsdev/Makefile.objs
> index 1b120a4..2c6da2d 100644
> --- a/fsdev/Makefile.objs
> +++ b/fsdev/Makefile.objs
> @@ -7,6 +7,7 @@ common-obj-y = qemu-fsdev-dummy.o
>  endif
>  common-obj-y += qemu-fsdev-opts.o
>  
> +common-obj-y += qemu-fsdev-throttle.o
>  # Toplevel always builds this; targets without virtio will put it in
>  # common-obj-y
>  common-obj-$(CONFIG_ALL) += qemu-fsdev-dummy.o
> diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
> index 6db9fea..33fe822 100644
> --- a/fsdev/file-op-9p.h
> +++ b/fsdev/file-op-9p.h
> @@ -17,6 +17,7 @@
>  #include <dirent.h>
>  #include <utime.h>
>  #include <sys/vfs.h>
> +#include "qemu-fsdev-throttle.h"
>  
>  #define SM_LOCAL_MODE_BITS    0600
>  #define SM_LOCAL_DIR_MODE_BITS    0700
> @@ -74,6 +75,7 @@ typedef struct FsDriverEntry {
>      char *path;
>      int export_flags;
>      FileOperations *ops;
> +    FsThrottle fst;
>  } FsDriverEntry;
>  
>  typedef struct FsContext
> @@ -83,6 +85,7 @@ typedef struct FsContext
>      int export_flags;
>      struct xattr_operations **xops;
>      struct extended_ops exops;
> +    FsThrottle *fst;
>      /* fs driver specific data */
>      void *private;
>  } FsContext;
> diff --git a/fsdev/qemu-fsdev-opts.c b/fsdev/qemu-fsdev-opts.c
> index 1dd8c7a..395d497 100644
> --- a/fsdev/qemu-fsdev-opts.c
> +++ b/fsdev/qemu-fsdev-opts.c
> @@ -37,6 +37,82 @@ static QemuOptsList qemu_fsdev_opts = {
>          }, {
>              .name = "sock_fd",
>              .type = QEMU_OPT_NUMBER,
> +        }, {
> +            .name = "throttling.iops-total",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "limit total I/O operations per second",
> +        },{
> +            .name = "throttling.iops-read",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "limit read operations per second",
> +        },{
> +            .name = "throttling.iops-write",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "limit write operations per second",
> +        },{
> +            .name = "throttling.bps-total",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "limit total bytes per second",
> +        },{
> +            .name = "throttling.bps-read",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "limit read bytes per second",
> +        },{
> +            .name = "throttling.bps-write",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "limit write bytes per second",
> +        },{
> +            .name = "throttling.iops-total-max",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "I/O operations burst",
> +        },{
> +            .name = "throttling.iops-read-max",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "I/O operations read burst",
> +        },{
> +            .name = "throttling.iops-write-max",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "I/O operations write burst",
> +        },{
> +            .name = "throttling.bps-total-max",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "total bytes burst",
> +        },{
> +            .name = "throttling.bps-read-max",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "total bytes read burst",
> +        },{
> +            .name = "throttling.bps-write-max",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "total bytes write burst",
> +        },{
> +            .name = "throttling.iops-total-max-length",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "length of the iops-total-max burst period, in seconds",
> +        },{
> +            .name = "throttling.iops-read-max-length",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "length of the iops-read-max burst period, in seconds",
> +        },{
> +            .name = "throttling.iops-write-max-length",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "length of the iops-write-max burst period, in seconds",
> +        },{
> +            .name = "throttling.bps-total-max-length",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "length of the bps-total-max burst period, in seconds",
> +        },{
> +            .name = "throttling.bps-read-max-length",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "length of the bps-read-max burst period, in seconds",
> +        },{
> +            .name = "throttling.bps-write-max-length",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "length of the bps-write-max burst period, in seconds",
> +        },{
> +            .name = "throttling.iops-size",
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "when limiting by iops max size of an I/O in bytes",
>          },
>  
>          { /*End of list */ }
> diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c
> new file mode 100644
> index 0000000..0adccd1
> --- /dev/null
> +++ b/fsdev/qemu-fsdev-throttle.c
> @@ -0,0 +1,191 @@
> +/*
> + * Fsdev Throttle
> + *
> + * Copyright (C) 2016 Huawei Technologies Duesseldorf GmbH
> + *
> + * Author: Pradeep Jagadeesh <pradeep.jagade...@huawei.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * (at your option) any later version.
> + *
> + * See the COPYING file in the top-level directory for details.
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/error-report.h"
> +#include "qapi/error.h"
> +#include "qemu-fsdev-throttle.h"
> +
> +static bool fsdev_throttle_check_for_wait(FsThrottle *fst, bool is_write)
> +{
> +    if (fst->any_timer_armed[is_write]) {
> +        return true;
> +    } else {
> +        return throttle_schedule_timer(&fst->ts, &fst->tt, is_write);
> +    }
> +}
> +
> +static void fsdev_throttle_schedule_next_request(FsThrottle *fst, bool 
> is_write)
> +{
> +    bool must_wait = fsdev_throttle_check_for_wait(fst, is_write);

Let's add a newline here.

> +    if (!fst->pending_reqs[is_write]) {
> +        return;
> +    }
> +    if (!must_wait) {
> +        if (qemu_in_coroutine() &&
> +            qemu_co_queue_next(&fst->throttled_reqs[is_write])) {
> +            ;
> +       } else {
> +           int64_t now = qemu_clock_get_ns(fst->tt.clock_type);
> +           timer_mod(fst->tt.timers[is_write], now + 1);
> +           fst->any_timer_armed[is_write] = true;
> +       }
> +   }
> +}
> +
> +static void fsdev_throttle_timer_cb(FsThrottle *fst, bool is_write)
> +{
> +    bool empty_queue;

Same here.

> +    qemu_mutex_lock(&fst->lock);
> +    fst->any_timer_armed[is_write] = false;
> +    qemu_mutex_unlock(&fst->lock);
> +    empty_queue = !qemu_co_enter_next(&fst->throttled_reqs[is_write]);
> +    if (empty_queue) {
> +        qemu_mutex_lock(&fst->lock);
> +        fsdev_throttle_schedule_next_request(fst, is_write);
> +        qemu_mutex_unlock(&fst->lock);
> +    }
> +}
> +
> +bool fsdev_throttle_enabled(FsThrottle *fst)
> +{
> +    return fst->enabled;
> +}
> +
> +static void fsdev_iolimits_enable(FsThrottle *fst)
> +{
> +    fst->enabled = true;
> +}
> +
> +static void fsdev_iolimits_disable(FsThrottle *fst)
> +{
> +    fst->enabled = false;
> +}
> +

fsdev_throttle_configure_iolimits() is the only function that will ever
write to fst->enabled. The helpers seem to indicate the opposite. It is
better to open code in fsdev_throttle_configure_iolimits().

> +static void fsdev_throttle_read_timer_cb(void *opaque)
> +{
> +    fsdev_throttle_timer_cb(opaque, false);
> +}
> +
> +static void fsdev_throttle_write_timer_cb(void *opaque)
> +{
> +    fsdev_throttle_timer_cb(opaque, true);
> +}
> +
> +static void fsdev_parse_io_limit_opts(QemuOpts *opts, FsThrottle *fst)
> +{
> +    fst->cfg.buckets[THROTTLE_BPS_TOTAL].avg =
> +          qemu_opt_get_number(opts, "throttling.bps-total", 0);
> +    fst->cfg.buckets[THROTTLE_BPS_READ].avg  =
> +          qemu_opt_get_number(opts, "throttling.bps-read", 0);
> +    fst->cfg.buckets[THROTTLE_BPS_WRITE].avg =
> +          qemu_opt_get_number(opts, "throttling.bps-write", 0);
> +    fst->cfg.buckets[THROTTLE_OPS_TOTAL].avg =
> +          qemu_opt_get_number(opts, "throttling.iops-total", 0);
> +    fst->cfg.buckets[THROTTLE_OPS_READ].avg =
> +          qemu_opt_get_number(opts, "throttling.iops-read", 0);
> +    fst->cfg.buckets[THROTTLE_OPS_WRITE].avg =
> +          qemu_opt_get_number(opts, "throttling.iops-write", 0);
> +
> +    fst->cfg.buckets[THROTTLE_BPS_TOTAL].max =
> +          qemu_opt_get_number(opts, "throttling.bps-total-max", 0);
> +    fst->cfg.buckets[THROTTLE_BPS_READ].max  =
> +          qemu_opt_get_number(opts, "throttling.bps-read-max", 0);
> +    fst->cfg.buckets[THROTTLE_BPS_WRITE].max =
> +          qemu_opt_get_number(opts, "throttling.bps-write-max", 0);
> +    fst->cfg.buckets[THROTTLE_OPS_TOTAL].max =
> +          qemu_opt_get_number(opts, "throttling.iops-total-max", 0);
> +    fst->cfg.buckets[THROTTLE_OPS_READ].max =
> +          qemu_opt_get_number(opts, "throttling.iops-read-max", 0);
> +    fst->cfg.buckets[THROTTLE_OPS_WRITE].max =
> +          qemu_opt_get_number(opts, "throttling.iops-write-max", 0);
> +
> +    fst->cfg.buckets[THROTTLE_BPS_TOTAL].burst_length =
> +          qemu_opt_get_number(opts, "throttling.bps-total-max-length", 1);
> +    fst->cfg.buckets[THROTTLE_BPS_READ].burst_length  =
> +          qemu_opt_get_number(opts, "throttling.bps-read-max-length", 1);
> +    fst->cfg.buckets[THROTTLE_BPS_WRITE].burst_length =
> +          qemu_opt_get_number(opts, "throttling.bps-write-max-length", 1);
> +    fst->cfg.buckets[THROTTLE_OPS_TOTAL].burst_length =
> +          qemu_opt_get_number(opts, "throttling.iops-total-max-length", 1);
> +    fst->cfg.buckets[THROTTLE_OPS_READ].burst_length =
> +          qemu_opt_get_number(opts, "throttling.iops-read-max-length", 1);
> +    fst->cfg.buckets[THROTTLE_OPS_WRITE].burst_length =
> +          qemu_opt_get_number(opts, "throttling.iops-write-max-length", 1);
> +    fst->cfg.op_size =
> +          qemu_opt_get_number(opts, "throttling.iops-size", 0);
> +}
> +
> +int fsdev_throttle_configure_iolimits(QemuOpts *opts, FsThrottle *fst)
> +{
> +    Error *err = NULL;
> +
> +    /* Parse and set populate the cfg structure */
> +    fsdev_parse_io_limit_opts(opts, fst);
> +
> +    if (!throttle_is_valid(&fst->cfg, &err)) {
> +        error_report("Throttle configuration is not valid");

throttle_is_valid() already populates err with a meaningful message and
you should use it:

        error_reportf_err(err, "Throttle configuration is not valid: ");

> +        return -1;
> +    }
> +    if (throttle_enabled(&fst->cfg)) {
> +        fst->aioctx = qemu_get_aio_context();
> +        if (!fst->aioctx) {
> +            error_report("Failed to create AIO Context");
> +            return -1;
> +        }

qemu_get_aio_context() returns qemu_aio_context which is initialized in
qemu_init_main_loop(). It is guarantied to be non NULL and if it is, we'd
better dump core.

> +        throttle_init(&fst->ts);
> +        throttle_timers_init(&fst->tt,
> +                             fst->aioctx,
> +                             QEMU_CLOCK_REALTIME,
> +                             fsdev_throttle_read_timer_cb,
> +                             fsdev_throttle_write_timer_cb,
> +                             fst);
> +        throttle_config(&fst->ts, &fst->tt, &fst->cfg);
> +        qemu_co_queue_init(&fst->throttled_reqs[0]);
> +        qemu_co_queue_init(&fst->throttled_reqs[1]);
> +        fst->pending_reqs[0] = 0;
> +        fst->pending_reqs[1] = 0;
> +        fst->any_timer_armed[0] = false;
> +        fst->any_timer_armed[1] = false;
> +        qemu_mutex_init(&fst->lock);
> +        fsdev_iolimits_enable(fst);
> +   } else {
> +        fsdev_iolimits_disable(fst);
> +   }
> +   return 0;
> +}
> +
> +void fsdev_throttle_request(FsThrottle *fst, bool is_write, ssize_t bytes)
> +{
> +    if (fsdev_throttle_enabled(fst)) {
> +        qemu_mutex_lock(&fst->lock);
> +        bool must_wait = fsdev_throttle_check_for_wait(fst, is_write);

Even if the QEMU code is supposed to follow C99, I think it is prettier to
declare variables at the beginning of the code block.

           bool must_wait;

           qemu_mutex_lock(&fst->lock);
           must_wait = fsdev_throttle_check_for_wait(fst, is_write);

> +        if (must_wait || fst->pending_reqs[is_write]) {
> +            fst->pending_reqs[is_write]++;
> +            qemu_mutex_unlock(&fst->lock);
> +            qemu_co_queue_wait(&fst->throttled_reqs[is_write]);
> +            qemu_mutex_lock(&fst->lock);
> +            fst->pending_reqs[is_write]--;
> +       }
> +       throttle_account(&fst->ts, is_write, bytes);
> +       fsdev_throttle_schedule_next_request(fst, is_write);
> +       qemu_mutex_unlock(&fst->lock);
> +    }
> +}
> +
> +void fsdev_throttle_cleanup(FsThrottle *fst)
> +{
> +    throttle_timers_destroy(&fst->tt);
> +    qemu_mutex_destroy(&fst->lock);
> +}
> diff --git a/fsdev/qemu-fsdev-throttle.h b/fsdev/qemu-fsdev-throttle.h
> new file mode 100644
> index 0000000..73dd367
> --- /dev/null
> +++ b/fsdev/qemu-fsdev-throttle.h
> @@ -0,0 +1,42 @@
> +/*
> + * Fsdev Throttle
> + *
> + * Copyright (C) 2016 Huawei Technologies Duesseldorf GmbH
> + *
> + * Author: Pradeep Jagadeesh <pradeep.jagade...@huawei.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * (at your option) any later version.
> + *
> + * See the COPYING file in the top-level directory for details.
> + *
> + */
> +
> +#ifndef _FSDEV_THROTTLE_H
> +#define _FSDEV_THROTTLE_H
> +
> +#include "block/aio.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/coroutine.h"
> +#include "qemu/throttle.h"
> +
> +typedef struct FsThrottle {
> +    ThrottleState ts;
> +    ThrottleTimers tt;
> +    AioContext   *aioctx;
> +    ThrottleConfig cfg;
> +    bool enabled;
> +    CoQueue      throttled_reqs[2];
> +    unsigned     pending_reqs[2];
> +    bool any_timer_armed[2];
> +    QemuMutex lock;
> +} FsThrottle;
> +
> +bool fsdev_throttle_enabled(FsThrottle *);
> +
> +int fsdev_throttle_configure_iolimits(QemuOpts *, FsThrottle *);
> +
> +void fsdev_throttle_request(FsThrottle *, bool , ssize_t);
> +
> +void fsdev_throttle_cleanup(FsThrottle *);
> +#endif /* _FSDEV_THROTTLE_H */
> diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> index 3f271fc..b1009fc 100644
> --- a/hw/9pfs/9p-local.c
> +++ b/hw/9pfs/9p-local.c
> @@ -436,8 +436,8 @@ static ssize_t local_pwritev(FsContext *ctx, 
> V9fsFidOpenState *fs,
>                               const struct iovec *iov,
>                               int iovcnt, off_t offset)
>  {
> -    ssize_t ret
> -;
> +    ssize_t ret;
> +
>  #ifdef CONFIG_PREADV
>      ret = pwritev(fs->fd, iov, iovcnt, offset);
>  #else
> @@ -1213,6 +1213,8 @@ static int local_parse_opts(QemuOpts *opts, struct 
> FsDriverEntry *fse)
>      const char *sec_model = qemu_opt_get(opts, "security_model");
>      const char *path = qemu_opt_get(opts, "path");
>  
> +    FsThrottle *fst = &fse->fst;
> +
>      if (!sec_model) {
>          error_report("Security model not specified, local fs needs security 
> model");
>          error_printf("valid options are:"
> @@ -1240,6 +1242,11 @@ static int local_parse_opts(QemuOpts *opts, struct 
> FsDriverEntry *fse)
>          error_report("fsdev: No path specified");
>          return -1;
>      }
> +
> +    if (fsdev_throttle_configure_iolimits(opts, fst) < 0) {
> +        return -1;
> +    }
> +
>      fse->path = g_strdup(path);
>  
>      return 0;
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index dfe293d..3748ba9 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -3490,6 +3490,10 @@ int v9fs_device_realize_common(V9fsState *s, Error 
> **errp)
>          error_setg(errp, "share path %s is not a directory", fse->path);
>          goto out;
>      }
> +
> +    /* Throttle structure initialization */

I'm still thinking this comment paraphrases the code :)

> +    s->ctx.fst = &fse->fst;
> +
>      v9fs_path_free(&path);
>  
>      rc = 0;
> @@ -3504,6 +3508,9 @@ out:
>  
>  void v9fs_device_unrealize_common(V9fsState *s, Error **errp)
>  {
> +    if (fsdev_throttle_enabled(s->ctx.fst)) {
> +        fsdev_throttle_cleanup(s->ctx.fst);
> +    }
>      g_free(s->ctx.fs_root);
>      g_free(s->tag);
>  }
> diff --git a/hw/9pfs/cofile.c b/hw/9pfs/cofile.c
> index 10343c0..65897d5 100644
> --- a/hw/9pfs/cofile.c
> +++ b/hw/9pfs/cofile.c
> @@ -16,6 +16,7 @@
>  #include "qemu/thread.h"
>  #include "qemu/coroutine.h"
>  #include "coth.h"
> +#include "fsdev/qemu-fsdev-throttle.h"
>  
>  int v9fs_co_st_gen(V9fsPDU *pdu, V9fsPath *path, mode_t st_mode,
>                     V9fsStatDotl *v9stat)
> @@ -242,6 +243,7 @@ int v9fs_co_pwritev(V9fsPDU *pdu, V9fsFidState *fidp,
>      int err;
>      V9fsState *s = pdu->s;
>  
> +    fsdev_throttle_request(s->ctx.fst, true, iov->iov_len);

I think it would make more sense to move this after the cancellation point.

>      if (v9fs_request_cancelled(pdu)) {
>          return -EINTR;
>      }
> @@ -261,6 +263,7 @@ int v9fs_co_preadv(V9fsPDU *pdu, V9fsFidState *fidp,
>      int err;
>      V9fsState *s = pdu->s;
>  
> +    fsdev_throttle_request(s->ctx.fst, false, iov->iov_len);

Same here.

>      if (v9fs_request_cancelled(pdu)) {
>          return -EINTR;
>      }

Cheers.

--
Greg

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