Hi Linus, Some more comments below.
On Mon, 5 Sep 2022 17:03:00 +0200 Linus Heckemann <g...@sphalerite.org> wrote: > 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 <g...@sphalerite.org> > --- > hw/9pfs/9p.c | 130 +++++++++++++++++++++++++++------------------------ > hw/9pfs/9p.h | 2 +- > 2 files changed, 69 insertions(+), 63 deletions(-) > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > index aebadeaa03..fb4b7fe852 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 +419,10 @@ 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; > - } > + if (g_hash_table_steal_extended(s->fids, GINT_TO_POINTER(fid), > + NULL, (gpointer *) &fidp)) { > + fidp->clunked = true; > + return fidp; > } > return NULL; > } > @@ -439,10 +432,15 @@ 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 > @@ -518,12 +516,11 @@ 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); > Using this external iterator API instead of the embedded QSIMPLEQ entry definitely simplifies logic. Thanks ! > /* > * v9fs_reopen_fid() can yield : a reference on the fid must be held > @@ -534,7 +531,13 @@ static int coroutine_fn v9fs_mark_fids_unreclaim(V9fsPDU > *pdu, V9fsPath *path) > * iteration after we could get a reference on the next fid. Start with > * the first one. > */ The comment above should be adapted to the new situation : no need to do anything special with the next fid since we're not getting a pointer to it before calling the "We're done with this fid" put_fid() on the current fid. > - for (fidp->ref++; fidp; fidp = fidp_next) { > + while (g_hash_table_iter_next(&iter, &fid, (gpointer *) &fidp)) { > + /* > + * Ensure the fid survives a potential clunk request during > + * put_fid() below and v9fs_reopen_fid() in the next iteration. With the new logic, this should just be: Ensure the fid survives a potential clunk request during v9fs_reopen_fid(). > + */ > + fidp->ref++; > + > if (fidp->path.size == path->size && > !memcmp(fidp->path.data, path->data, path->size)) { > /* Mark the fid non reclaimable. */ > @@ -548,16 +551,6 @@ 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); > } > @@ -569,19 +562,21 @@ 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); You could just call g_hash_table_iter_remove(&iter) here (it is safe according to the glib documentation [1]) and... > fidp->clunked = true; > > put_fid(pdu, fidp); > } > + g_hash_table_remove_all(s->fids); ... avoid the extra loop, but no big deal. Rest looks ok. Please re-post and add: Reviewed-by: Greg Kurz <gr...@kaod.org> Don't forget to put a v3 in the subject and provide the list of changes since v2 below the '---' terminator of the commit message (see [2] for an example). You might want to try out 'git publish' [3], a marvelous tool that helps a lot with the tedious process of posting versionned patch series. Cheers, -- Greg [1] https://developer-old.gnome.org/glib/stable/glib-Hash-Tables.html#g-hash-table-iter-remove [2] https://patchwork.ozlabs.org/project/qemu-devel/patch/20210121181510.1459390-1-gr...@kaod.org/ [3] https://github.com/stefanha/git-publish > } > > #define P9_QID_TYPE_DIR 0x80 > @@ -3205,6 +3200,8 @@ 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 +3235,13 @@ 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 +3319,8 @@ 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 +3337,8 @@ 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 +4228,7 @@ 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 +4288,10 @@ 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;