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[PATCH v3] 9pfs: use GHashTable for fid table
From: |
Linus Heckemann |
Subject: |
[PATCH v3] 9pfs: use GHashTable for fid table |
Date: |
Thu, 8 Sep 2022 13:23:53 +0200 |
The previous implementation would iterate over the fid table for
lookup operations, resulting in an operation with O(n) complexity on
the number of open files and poor cache locality -- for every open,
stat, read, write, etc operation.
This change uses a hashtable for this instead, significantly improving
the performance of the 9p filesystem. The runtime of NixOS's simple
installer test, which copies ~122k files totalling ~1.8GiB from 9p,
decreased by a factor of about 10.
Signed-off-by: Linus Heckemann <git@sphalerite.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
---
Greg Kurz writes:
> The comment above should be adapted to the new situation : no need
I've removed it completely, since the logic is simple enough that only
the shortened comment below remains necessary.
> With the new logic, this should just be:
now is :)
> g_hash_table_steal_extended() [1] actually allows to do just that.
g_hash_table_steal_extended unfortunately isn't available since it was
introduced in glib 2.58 and we're maintaining compatibility to 2.56.
> You could just call g_hash_table_iter_remove(&iter) here
Applied this suggestion, thanks!
> Well... finding at least one clunked fid state in this table is
> definitely a bug so I'll keep the BUG_ON() anyway.
Christian Schoenebeck writes:
> Yeah, I think you are right, it would feel odd. Just drop BUG_ON() for
> now.
I still prefer dropping it, but if we were to keep it I think it should
be in v9fs_reclaim_fd where we iterate and can thus check the whole
table.
Greg Kurz and Philippe Mathieu-Daudé write:
> [patch versioning]
Whoops. I used -v2 on git send-email, which just ignored the option,
rather than git format-patch, by accident. This one _should_ now be v3!
hw/9pfs/9p.c | 140 +++++++++++++++++++++++++--------------------------
hw/9pfs/9p.h | 2 +-
2 files changed, 70 insertions(+), 72 deletions(-)
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index aebadeaa03..98a475e560 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -282,33 +282,31 @@ static V9fsFidState *coroutine_fn get_fid(V9fsPDU *pdu,
int32_t fid)
V9fsFidState *f;
V9fsState *s = pdu->s;
- QSIMPLEQ_FOREACH(f, &s->fid_list, next) {
- BUG_ON(f->clunked);
- if (f->fid == fid) {
- /*
- * Update the fid ref upfront so that
- * we don't get reclaimed when we yield
- * in open later.
- */
- f->ref++;
- /*
- * check whether we need to reopen the
- * file. We might have closed the fd
- * while trying to free up some file
- * descriptors.
- */
- err = v9fs_reopen_fid(pdu, f);
- if (err < 0) {
- f->ref--;
- return NULL;
- }
- /*
- * Mark the fid as referenced so that the LRU
- * reclaim won't close the file descriptor
- */
- f->flags |= FID_REFERENCED;
- return f;
+ f = g_hash_table_lookup(s->fids, GINT_TO_POINTER(fid));
+ if (f) {
+ /*
+ * Update the fid ref upfront so that
+ * we don't get reclaimed when we yield
+ * in open later.
+ */
+ f->ref++;
+ /*
+ * check whether we need to reopen the
+ * file. We might have closed the fd
+ * while trying to free up some file
+ * descriptors.
+ */
+ err = v9fs_reopen_fid(pdu, f);
+ if (err < 0) {
+ f->ref--;
+ return NULL;
}
+ /*
+ * Mark the fid as referenced so that the LRU
+ * reclaim won't close the file descriptor
+ */
+ f->flags |= FID_REFERENCED;
+ return f;
}
return NULL;
}
@@ -317,12 +315,9 @@ static V9fsFidState *alloc_fid(V9fsState *s, int32_t fid)
{
V9fsFidState *f;
- QSIMPLEQ_FOREACH(f, &s->fid_list, next) {
+ if (g_hash_table_contains(s->fids, GINT_TO_POINTER(fid))) {
/* If fid is already there return NULL */
- BUG_ON(f->clunked);
- if (f->fid == fid) {
- return NULL;
- }
+ return NULL;
}
f = g_new0(V9fsFidState, 1);
f->fid = fid;
@@ -333,7 +328,7 @@ static V9fsFidState *alloc_fid(V9fsState *s, int32_t fid)
* reclaim won't close the file descriptor
*/
f->flags |= FID_REFERENCED;
- QSIMPLEQ_INSERT_TAIL(&s->fid_list, f, next);
+ g_hash_table_insert(s->fids, GINT_TO_POINTER(fid), f);
v9fs_readdir_init(s->proto_version, &f->fs.dir);
v9fs_readdir_init(s->proto_version, &f->fs_reclaim.dir);
@@ -424,12 +419,11 @@ static V9fsFidState *clunk_fid(V9fsState *s, int32_t fid)
{
V9fsFidState *fidp;
- QSIMPLEQ_FOREACH(fidp, &s->fid_list, next) {
- if (fidp->fid == fid) {
- QSIMPLEQ_REMOVE(&s->fid_list, fidp, V9fsFidState, next);
- fidp->clunked = true;
- return fidp;
- }
+ fidp = g_hash_table_lookup(s->fids, GINT_TO_POINTER(fid));
+ if (fidp) {
+ g_hash_table_remove(s->fids, GINT_TO_POINTER(fid));
+ fidp->clunked = true;
+ return fidp;
}
return NULL;
}
@@ -439,10 +433,15 @@ void coroutine_fn v9fs_reclaim_fd(V9fsPDU *pdu)
int reclaim_count = 0;
V9fsState *s = pdu->s;
V9fsFidState *f;
+ GHashTableIter iter;
+ gpointer fid;
+
+ g_hash_table_iter_init(&iter, s->fids);
+
QSLIST_HEAD(, V9fsFidState) reclaim_list =
QSLIST_HEAD_INITIALIZER(reclaim_list);
- QSIMPLEQ_FOREACH(f, &s->fid_list, next) {
+ while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &f)) {
/*
* Unlink fids cannot be reclaimed. Check
* for them and skip them. Also skip fids
@@ -518,23 +517,19 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU
*pdu, V9fsPath *path)
{
int err;
V9fsState *s = pdu->s;
- V9fsFidState *fidp, *fidp_next;
+ V9fsFidState *fidp;
+ gpointer fid;
+ GHashTableIter iter;
- fidp = QSIMPLEQ_FIRST(&s->fid_list);
- if (!fidp) {
- return 0;
- }
+ g_hash_table_iter_init(&iter, s->fids);
+
+ while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &fidp)) {
+ /*
+ * Ensure the fid survives a potential clunk request during
+ * v9fs_reopen_fid.
+ */
+ fidp->ref++;
- /*
- * v9fs_reopen_fid() can yield : a reference on the fid must be held
- * to ensure its pointer remains valid and we can safely pass it to
- * QSIMPLEQ_NEXT(). The corresponding put_fid() can also yield so
- * we must keep a reference on the next fid as well. So the logic here
- * is to get a reference on a fid and only put it back during the next
- * iteration after we could get a reference on the next fid. Start with
- * the first one.
- */
- for (fidp->ref++; fidp; fidp = fidp_next) {
if (fidp->path.size == path->size &&
!memcmp(fidp->path.data, path->data, path->size)) {
/* Mark the fid non reclaimable. */
@@ -548,16 +543,6 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU
*pdu, V9fsPath *path)
}
}
- fidp_next = QSIMPLEQ_NEXT(fidp, next);
-
- if (fidp_next) {
- /*
- * Ensure the next fid survives a potential clunk request during
- * put_fid() below and v9fs_reopen_fid() in the next iteration.
- */
- fidp_next->ref++;
- }
-
/* We're done with this fid */
put_fid(pdu, fidp);
}
@@ -569,18 +554,20 @@ static void coroutine_fn virtfs_reset(V9fsPDU *pdu)
{
V9fsState *s = pdu->s;
V9fsFidState *fidp;
+ gpointer fid;
+ GHashTableIter iter;
+
+ g_hash_table_iter_init(&iter, s->fids);
/* Free all fids */
- while (!QSIMPLEQ_EMPTY(&s->fid_list)) {
- /* Get fid */
- fidp = QSIMPLEQ_FIRST(&s->fid_list);
+ while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &fidp)) {
fidp->ref++;
/* Clunk fid */
- QSIMPLEQ_REMOVE(&s->fid_list, fidp, V9fsFidState, next);
fidp->clunked = true;
put_fid(pdu, fidp);
+ g_hash_table_iter_remove(&iter);
}
}
@@ -3205,6 +3192,8 @@ static int coroutine_fn v9fs_complete_rename(V9fsPDU
*pdu, V9fsFidState *fidp,
V9fsFidState *tfidp;
V9fsState *s = pdu->s;
V9fsFidState *dirfidp = NULL;
+ GHashTableIter iter;
+ gpointer fid;
v9fs_path_init(&new_path);
if (newdirfid != -1) {
@@ -3238,11 +3227,13 @@ static int coroutine_fn v9fs_complete_rename(V9fsPDU
*pdu, V9fsFidState *fidp,
if (err < 0) {
goto out;
}
+
/*
* Fixup fid's pointing to the old name to
* start pointing to the new name
*/
- QSIMPLEQ_FOREACH(tfidp, &s->fid_list, next) {
+ g_hash_table_iter_init(&iter, s->fids);
+ while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &tfidp)) {
if (v9fs_path_is_ancestor(&fidp->path, &tfidp->path)) {
/* replace the name */
v9fs_fix_path(&tfidp->path, &new_path, strlen(fidp->path.data));
@@ -3320,6 +3311,8 @@ static int coroutine_fn v9fs_fix_fid_paths(V9fsPDU *pdu,
V9fsPath *olddir,
V9fsPath oldpath, newpath;
V9fsState *s = pdu->s;
int err;
+ GHashTableIter iter;
+ gpointer fid;
v9fs_path_init(&oldpath);
v9fs_path_init(&newpath);
@@ -3336,7 +3329,8 @@ static int coroutine_fn v9fs_fix_fid_paths(V9fsPDU *pdu,
V9fsPath *olddir,
* Fixup fid's pointing to the old name to
* start pointing to the new name
*/
- QSIMPLEQ_FOREACH(tfidp, &s->fid_list, next) {
+ g_hash_table_iter_init(&iter, s->fids);
+ while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &tfidp)) {
if (v9fs_path_is_ancestor(&oldpath, &tfidp->path)) {
/* replace the name */
v9fs_fix_path(&tfidp->path, &newpath, strlen(oldpath.data));
@@ -4226,7 +4220,7 @@ int v9fs_device_realize_common(V9fsState *s, const
V9fsTransport *t,
s->ctx.fmode = fse->fmode;
s->ctx.dmode = fse->dmode;
- QSIMPLEQ_INIT(&s->fid_list);
+ s->fids = g_hash_table_new(NULL, NULL);
qemu_co_rwlock_init(&s->rename_lock);
if (s->ops->init(&s->ctx, errp) < 0) {
@@ -4286,6 +4280,10 @@ void v9fs_device_unrealize_common(V9fsState *s)
if (s->ctx.fst) {
fsdev_throttle_cleanup(s->ctx.fst);
}
+ if (s->fids) {
+ g_hash_table_destroy(s->fids);
+ s->fids = NULL;
+ }
g_free(s->tag);
qp_table_destroy(&s->qpd_table);
qp_table_destroy(&s->qpp_table);
diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index 994f952600..10fd2076c2 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -339,7 +339,7 @@ typedef struct {
struct V9fsState {
QLIST_HEAD(, V9fsPDU) free_list;
QLIST_HEAD(, V9fsPDU) active_list;
- QSIMPLEQ_HEAD(, V9fsFidState) fid_list;
+ GHashTable *fids;
FileOperations *ops;
FsContext ctx;
char *tag;
--
2.36.0
- [PATCH v3] 9pfs: use GHashTable for fid table,
Linus Heckemann <=