Messages in this thread | | | Date | Wed, 14 Jun 2023 11:59:28 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH V11 08/10] arm64/perf: Add struct brbe_regset helper functions |
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On Wed, Jun 14, 2023 at 10:44:38AM +0530, Anshuman Khandual wrote: > On 6/13/23 22:47, Mark Rutland wrote: > >> +/* > >> + * This scans over BRBE register banks and captures individual branch reocrds > >> + * [BRBSRC, BRBTGT, BRBINF] into a pre-allocated 'struct brbe_regset' buffer, > >> + * until an invalid one gets encountered. The caller for this function needs > >> + * to ensure BRBE is an appropriate state before the records can be captured. > >> + */ > >> +static int capture_brbe_regset(struct brbe_hw_attr *brbe_attr, struct brbe_regset *buf) > >> +{ > >> + int loop1_idx1, loop1_idx2, loop2_idx1, loop2_idx2; > >> + int idx, count; > >> + > >> + loop1_idx1 = BRBE_BANK0_IDX_MIN; > >> + if (brbe_attr->brbe_nr <= BRBE_BANK_MAX_ENTRIES) { > >> + loop1_idx2 = brbe_attr->brbe_nr - 1; > >> + loop2_idx1 = BRBE_BANK1_IDX_MIN; > >> + loop2_idx2 = BRBE_BANK0_IDX_MAX; > >> + } else { > >> + loop1_idx2 = BRBE_BANK0_IDX_MAX; > >> + loop2_idx1 = BRBE_BANK1_IDX_MIN; > >> + loop2_idx2 = brbe_attr->brbe_nr - 1; > >> + } > >> + > >> + select_brbe_bank(BRBE_BANK_IDX_0); > >> + for (idx = 0, count = loop1_idx1; count <= loop1_idx2; idx++, count++) { > >> + buf[idx].brbinf = get_brbinf_reg(idx); > >> + /* > >> + * There are no valid entries anymore on the buffer. > >> + * Abort the branch record processing to save some > >> + * cycles and also reduce the capture/process load > >> + * for the user space as well. > >> + */ > >> + if (brbe_invalid(buf[idx].brbinf)) > >> + return idx; > >> + > >> + buf[idx].brbsrc = get_brbsrc_reg(idx); > >> + buf[idx].brbtgt = get_brbtgt_reg(idx); > >> + } > >> + > >> + select_brbe_bank(BRBE_BANK_IDX_1); > >> + for (count = loop2_idx1; count <= loop2_idx2; idx++, count++) { > >> + buf[idx].brbinf = get_brbinf_reg(idx); > >> + /* > >> + * There are no valid entries anymore on the buffer. > >> + * Abort the branch record processing to save some > >> + * cycles and also reduce the capture/process load > >> + * for the user space as well. > >> + */ > >> + if (brbe_invalid(buf[idx].brbinf)) > >> + return idx; > >> + > >> + buf[idx].brbsrc = get_brbsrc_reg(idx); > >> + buf[idx].brbtgt = get_brbtgt_reg(idx); > >> + } > >> + return idx; > >> +} > > > > As with __armv8pmu_branch_read(), the loop conditions are a bit hard to follow, > > and I believe that can be rewritten along the lines of the suggestion there. > > I have changed both the places (in separate patches) with suggested loop structure. > > > > > Looking at this, we now have a couple of places that will try to read the > > registers for an individual record, so it probably makes sense to facotr that > > into a helper, e.g. > > There are indeed two places inside capture_brbe_regset() - one for each bank. > > > > > | static bool __read_brbe_regset(struct brbe_regset *entry, int idx) > > | { > > | u64 brbinf = get_brbinf_reg(idx); > > | > > | if (brbe_invalid(brbinf)) > > | return false; > > | > > | entry->brbinf = brbinf; > > | entry->brbsrc = get_brbsrc_reg(idx); > > | entry->brbtgt = get_brbtgt_reg(idx); > > | > > | return true; > > | } > > > > ... which can be used here, e.g. > > > > | /* > > | * Capture all records before the first invalid record, and return the number > > | * of records captured. > > | */ > > | static int capture_brbe_regset(struct brbe_hw_attr *brbe_attr, struct brbe_regset *buf) > > | { > > | > > | int nr_entries = brbe_attr->brbe_nr; > > | int idx = 0; > > | > > | select_brbe_bank(BRBE_BANK_IDX_0); > > | while (idx < nr_entries && IDX < BRBE_BANK0_IDX_MAX) { > > | if (__read_brbe_regset(&buf[idx], idx)) > > It should test !_read_brbe_regset(&buf[idx], idx)) instead as the error > case returns false.
Yes, my bad.
> >> +static int stitch_stored_live_entries(struct brbe_regset *stored, > >> + struct brbe_regset *live, > >> + int nr_stored, int nr_live, > >> + int nr_max) > >> +{ > >> + int nr_total, nr_excess, nr_last, i; > >> + > >> + nr_total = nr_stored + nr_live; > >> + nr_excess = nr_total - nr_max; > >> + > >> + /* Stored branch records in stitched buffer */ > >> + if (nr_live == nr_max) > >> + nr_stored = 0; > >> + else if (nr_excess > 0) > >> + nr_stored -= nr_excess; > >> + > >> + /* Stitched buffer branch records length */ > >> + if (nr_total > nr_max) > >> + nr_last = nr_max; > >> + else > >> + nr_last = nr_total; > >> + > >> + /* Move stored branch records */ > >> + for (i = 0; i < nr_stored; i++) > >> + copy_brbe_regset(stored, i, stored, nr_last - nr_stored - 1 + i); > >> + > >> + /* Copy live branch records */ > >> + for (i = 0; i < nr_live; i++) > >> + copy_brbe_regset(live, i, stored, i); > >> + > >> + return nr_last; > >> +} > > > > I think this can be written more simply as something like: > > > > static int stitch_stored_live_entries(struct brbe_regset *stored, > > struct brbe_regset *live, > > int nr_stored, int nr_live, > > int nr_max) > > { > > int nr_move = max(nr_stored, nr_max - nr_live); > > Should this compare be min() instead ?
Yup, my bad again. That should be min().
> > /* Move the tail of the buffer to make room for the new entries */ > > memmove(&stored[nr_live], &stored[0], nr_move * sizeof(*stored)); > > > > /* Copy the new entries into the head of the buffer */ > > memcpy(stored[0], &live[0], nr_live * sizeof(*stored)); > > > > /* Return the number of entries in the stitched buffer */ > > return min(nr_live + nr_stored, nr_max); > > } > > Otherwise this makes sense and simpler, will rework.
Great!
Thanks, Mark.
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