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Re: [Qemu-devel] [PATCH v1 1/1] block/gluster: memory usage: use one glf
From: |
Jeff Cody |
Subject: |
Re: [Qemu-devel] [PATCH v1 1/1] block/gluster: memory usage: use one glfs instance per volume |
Date: |
Thu, 27 Oct 2016 09:08:51 -0400 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Thu, Oct 27, 2016 at 04:16:03PM +0530, Prasanna Kumar Kalever wrote:
> Currently, for every drive accessed via gfapi we create a new glfs
> instance (call glfs_new() followed by glfs_init()) which could consume
> memory in few 100 MB's, from the table below it looks like for each
> instance ~300 MB VSZ was consumed
>
> Before:
> -------
> Disks VSZ RSS
> 1 1098728 187756
> 2 1430808 198656
> 3 1764932 199704
> 4 2084728 202684
>
> This patch maintains a list of pre-opened glfs objects. On adding
> a new drive belonging to the same gluster volume, we just reuse the
> existing glfs object by updating its refcount.
>
> With this approch we shrink up the unwanted memory consumption and
> glfs_new/glfs_init calls for accessing a disk (file) if belongs to
> same volume.
>
> From below table notice that the memory usage after adding a disk
> (which will reuse the existing glfs object hence) is in negligible
> compared to before.
>
> After:
> ------
> Disks VSZ RSS
> 1 1101964 185768
> 2 1109604 194920
> 3 1114012 196036
> 4 1114496 199868
>
> Disks: number of -drive
> VSZ: virtual memory size of the process in KiB
> RSS: resident set size, the non-swapped physical memory (in kiloBytes)
>
> VSZ and RSS are analyzed using 'ps aux' utility.
>
> Signed-off-by: Prasanna Kumar Kalever <address@hidden>
> ---
> block/gluster.c | 105
> ++++++++++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 91 insertions(+), 14 deletions(-)
>
> diff --git a/block/gluster.c b/block/gluster.c
> index 01b479f..367d692 100644
> --- a/block/gluster.c
> +++ b/block/gluster.c
> @@ -54,6 +54,19 @@ typedef struct BDRVGlusterReopenState {
> } BDRVGlusterReopenState;
>
>
> +typedef struct GlfsPreopened {
> + char *volume;
> + glfs_t *fs;
> + int ref;
> +} GlfsPreopened;
> +
> +typedef struct ListElement {
> + QLIST_ENTRY(ListElement) list;
> + GlfsPreopened saved;
> +} ListElement;
> +
> +static QLIST_HEAD(glfs_list, ListElement) glfs_list;
> +
> static QemuOptsList qemu_gluster_create_opts = {
> .name = "qemu-gluster-create-opts",
> .head = QTAILQ_HEAD_INITIALIZER(qemu_gluster_create_opts.head),
> @@ -182,6 +195,63 @@ static QemuOptsList runtime_tcp_opts = {
> },
> };
>
> +static int glfs_set_preopened(const char *volume, glfs_t *fs)
> +{
> + ListElement *entry = NULL;
> +
> + entry = g_new(ListElement, 1);
> + if (!entry) {
This NULL check is not needed, g_new is guaranteed to succeed if it returns.
If any glib allocation function fails, it will abort and terminate the
application (it is considered a fatal error). So the QEMU coding convention
is to not check for NULL after glib allocation functions. The exception to
this are the g_try_* functions, of course.
> + errno = ENOMEM;
> + return -1;
> + }
> +
> + entry->saved.volume = g_strdup(volume);
> + if (!entry->saved.volume) {
Same here.
> + g_free(entry->saved.volume);
> + errno = ENOMEM;
> + return -1;
> + }
> +
> + entry->saved.fs = fs;
> + entry->saved.ref = 1;
> +
> + QLIST_INSERT_HEAD(&glfs_list, entry, list);
> +
> + return 0;
Without the need for memory error checking, this function can just return
void.
> +}
> +
> +static glfs_t *glfs_find_preopened(const char *volume)
> +{
> + ListElement *entry = NULL;
> +
> + QLIST_FOREACH(entry, &glfs_list, list) {
> + if (strcmp(entry->saved.volume, volume) == 0) {
> + entry->saved.ref++;
> + return entry->saved.fs;
> + }
> + }
> +
> + return NULL;
> +}
> +
> +static void glfs_clear_preopened(glfs_t *fs)
> +{
> + ListElement *entry = NULL;
> +
Maybe short circuit with a return if fs==NULL?
> + QLIST_FOREACH(entry, &glfs_list, list) {
> + if (entry->saved.fs == fs) {
> + if (--entry->saved.ref) {
> + return;
> + }
> +
> + QLIST_REMOVE(entry, list);
> +
> + glfs_fini(entry->saved.fs);
You need to g_free(entry->saved.volume) as well.
> + g_free(entry);
> + }
> + }
> +}
> +
> static int parse_volume_options(BlockdevOptionsGluster *gconf, char *path)
> {
> char *p, *q;
> @@ -319,11 +389,23 @@ static struct glfs
> *qemu_gluster_glfs_init(BlockdevOptionsGluster *gconf,
> int old_errno;
> GlusterServerList *server;
>
> + glfs = glfs_find_preopened(gconf->volume);
> + if (glfs) {
> + return glfs;
> + }
> +
> glfs = glfs_new(gconf->volume);
> if (!glfs) {
> goto out;
> }
>
> + ret = glfs_set_preopened(gconf->volume, glfs);
> + if (ret < 0) {
> + error_setg(errp, "glfs_set_preopened: Failed to register volume
> (%s)",
> + gconf->volume);
> + goto out;
> + }
> +
> for (server = gconf->server; server; server = server->next) {
> if (server->value->type == GLUSTER_TRANSPORT_UNIX) {
> ret = glfs_set_volfile_server(glfs,
> @@ -375,7 +457,7 @@ static struct glfs
> *qemu_gluster_glfs_init(BlockdevOptionsGluster *gconf,
> out:
> if (glfs) {
> old_errno = errno;
> - glfs_fini(glfs);
> + glfs_clear_preopened(glfs);
> errno = old_errno;
> }
> return NULL;
> @@ -741,9 +823,9 @@ out:
> if (s->fd) {
> glfs_close(s->fd);
> }
> - if (s->glfs) {
> - glfs_fini(s->glfs);
> - }
> +
> + glfs_clear_preopened(s->glfs);
> +
> return ret;
> }
>
> @@ -808,9 +890,8 @@ static void qemu_gluster_reopen_commit(BDRVReopenState
> *state)
> if (s->fd) {
> glfs_close(s->fd);
> }
> - if (s->glfs) {
> - glfs_fini(s->glfs);
> - }
> +
> + glfs_clear_preopened(s->glfs);
>
> /* use the newly opened image / connection */
> s->fd = reop_s->fd;
> @@ -835,9 +916,7 @@ static void qemu_gluster_reopen_abort(BDRVReopenState
> *state)
> glfs_close(reop_s->fd);
> }
>
> - if (reop_s->glfs) {
> - glfs_fini(reop_s->glfs);
> - }
> + glfs_clear_preopened(reop_s->glfs);
>
> g_free(state->opaque);
> state->opaque = NULL;
> @@ -955,9 +1034,7 @@ static int qemu_gluster_create(const char *filename,
> out:
> g_free(tmp);
> qapi_free_BlockdevOptionsGluster(gconf);
> - if (glfs) {
> - glfs_fini(glfs);
> - }
> + glfs_clear_preopened(glfs);
> return ret;
> }
>
> @@ -1029,7 +1106,7 @@ static void qemu_gluster_close(BlockDriverState *bs)
> glfs_close(s->fd);
> s->fd = NULL;
> }
> - glfs_fini(s->glfs);
> + glfs_clear_preopened(s->glfs);
> }
>
> static coroutine_fn int qemu_gluster_co_flush_to_disk(BlockDriverState *bs)
> --
> 2.7.4
>