Github/littlefs
1
Fork 0
Code Actions Activity

t: Limited lfs3_alloc_ckpoint to LFS3_T_LOOKAHEAD

Browse Source 
This was causing a problem where the bmap was being rebuilt on every
lfs3_trv_read, even though the traversal was opened LFS3_T_RDONLY!

Also added a note on why we don't need to traverse both the active and
on-disk bmaps. Counterintuitively, we don't need to because the new bmap
always contains the entirety of the on-disk bmap.

Code changes minimal:

                code          stack          ctx
  before:      36840           2368          684
  after:       36856 (+0.0%)   2368 (+0.0%)  684 (+0.0%)

                code          stack          ctx
  bmap before: 38440           2400          812
  bmap after:  38452 (+0.0%)   2400 (+0.0%)  812 (+0.0%)
This commit is contained in:
Christopher Haster
2025-08-03 13:09:04 -05:00
parent 507c04db70
commit 18d1f68445
1 changed files with 27 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lfs3.c
+27 -6
View File
@@ -10284,6 +10284,11 @@ static lfs3_stag_t lfs3_mtree_traverse_(lfs3_t *lfs3, lfs3_trv_t *trv,
lfs3_t_settstate(&trv->b.h.flags, LFS3_TSTATE_HANDLES);
continue;
// end of bmap? guess we're done
//
// note that new bmaps _always_ contains the entirety of
// the previous bmap, this avoids needing to traverse
// both the on-disk bmap and active bmap for things like
// lookahead scans
} else if (lfs3_t_tstate(trv->b.h.flags)
== LFS3_TSTATE_BMAP) {
lfs3_t_settstate(&trv->b.h.flags, LFS3_TSTATE_DONE);
@@ -11369,6 +11374,10 @@ static int lfs3_alloc_rebuildbmap(lfs3_t *lfs3) {
// this avoids extra writing at a risk of needing to reconstruct the
// bmap if we lose power
//
// note that new bmaps _always_ contains the entirety of the
// previous bmap, this avoids needing to traverse both the on-disk
// bmap and active bmap for things like lookahead scans
//
// don't worry about window/known, lfs3_mdir_commit updates these
// last minute before calculating gdeltas for a commit
lfs3->lookahead.bmapped = lfs3->lookahead.ckpoint;
@@ -16818,10 +16827,16 @@ static int lfs3_fs_gc_(lfs3_t *lfs3, lfs3_trv_t *trv,
while (pending && (lfs3_off_t)steps > 0) {
// checkpoint the allocator to maximize any lookahead scans
//
// TODO how does the bmap interact with LFS3_T_LOOKAHEAD? Should
// we populate it? use a different flag?
//
#ifndef LFS3_RDONLY
int err = lfs3_alloc_ckpoint(lfs3);
if (err) {
return err;
if (lfs3_t_islookahead(trv->b.h.flags)) {
int err = lfs3_alloc_ckpoint(lfs3);
if (err) {
return err;
}
}
#endif
@@ -17059,10 +17074,16 @@ int lfs3_trv_read(lfs3_t *lfs3, lfs3_trv_t *trv,
#endif
// checkpoint the allocator to maximize any lookahead scans
//
// TODO how does the bmap interact with LFS3_T_LOOKAHEAD? Should
// we populate it? use a different flag?
//
#ifndef LFS3_RDONLY
int err = lfs3_alloc_ckpoint(lfs3);
if (err) {
return err;
if (lfs3_t_islookahead(trv->b.h.flags)) {
int err = lfs3_alloc_ckpoint(lfs3);
if (err) {
return err;
}
}
#endif