On Thu, Oct 27, 2016 at 6:38 PM, Jeff Cody <jc...@redhat.com> wrote:
> 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 <prasanna.kale...@redhat.com>
>> ---
>> 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.
Perfect!
Will remove the defense checks for glib allocations through out the patch.
>
>
>> + 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.
yes.
>
>> +}
>> +
>> +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?
Worth one.
>
>> + 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.
You caught it ;)
Thanks Jeff, will accommodate all the suggestions in the next spin.
--
Prasanna
>
>> + 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
>>
