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| author | Vladimir Oltean <vladimir.oltean@nxp.com> | 2023-03-21 03:03:23 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-03-21 21:27:10 -0700 |
| commit | 6acc72a43eac78a309160d0a7512bbc59bcdd757 (patch) | |
| tree | 2c6eb4ec6b4a4dc5eda1d43a07597f04ac16eeb7 /drivers/net/ethernet | |
| parent | 8e50ed774554f93d55426039b27b1e38d7fa64d8 (diff) | |
net: mscc: ocelot: fix stats region batching
The blamed commit changed struct ocelot_stat_layout :: "u32 offset" to
"u32 reg".
However, "u32 reg" is not quite a register address, but an enum
ocelot_reg, which in itself encodes an enum ocelot_target target in the
upper bits, and an index into the ocelot->map[target][] array in the
lower bits.
So, whereas the previous code comparison between stats_layout[i].offset
and last + 1 was correct (because those "offsets" at the time were
32-bit relative addresses), the new code, comparing layout[i].reg to
last + 4 is not correct, because the "reg" here is an enum/index, not an
actual register address.
What we want to compare are indeed register addresses, but to do that,
we need to actually go through the same motions as
__ocelot_bulk_read_ix() itself.
With this bug, all statistics counters are deemed by
ocelot_prepare_stats_regions() as constituting their own region.
(Truncated) log on VSC9959 (Felix) below (prints added by me):
Before:
region of 1 contiguous counters starting with SYS:STAT:CNT[0x000]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x001]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x002]
...
region of 1 contiguous counters starting with SYS:STAT:CNT[0x041]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x042]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x080]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x081]
...
region of 1 contiguous counters starting with SYS:STAT:CNT[0x0ac]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x100]
region of 1 contiguous counters starting with SYS:STAT:CNT[0x101]
...
region of 1 contiguous counters starting with SYS:STAT:CNT[0x111]
After:
region of 67 contiguous counters starting with SYS:STAT:CNT[0x000]
region of 45 contiguous counters starting with SYS:STAT:CNT[0x080]
region of 18 contiguous counters starting with SYS:STAT:CNT[0x100]
Since commit d87b1c08f38a ("net: mscc: ocelot: use bulk reads for
stats") intended bulking as a performance improvement, and since now,
with trivial-sized regions, performance is even worse than without
bulking at all, this could easily qualify as a performance regression.
Fixes: d4c367650704 ("net: mscc: ocelot: keep ocelot_stat_layout by reg address, not offset")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Colin Foster <colin.foster@in-advantage.com>
Tested-by: Colin Foster <colin.foster@in-advantage.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers/net/ethernet')
| -rw-r--r-- | drivers/net/ethernet/mscc/ocelot_stats.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/net/ethernet/mscc/ocelot_stats.c b/drivers/net/ethernet/mscc/ocelot_stats.c index bdb893476832..096c81ec9dd6 100644 --- a/drivers/net/ethernet/mscc/ocelot_stats.c +++ b/drivers/net/ethernet/mscc/ocelot_stats.c @@ -899,7 +899,8 @@ static int ocelot_prepare_stats_regions(struct ocelot *ocelot) if (!layout[i].reg) continue; - if (region && layout[i].reg == last + 4) { + if (region && ocelot->map[SYS][layout[i].reg & REG_MASK] == + ocelot->map[SYS][last & REG_MASK] + 4) { region->count++; } else { region = devm_kzalloc(ocelot->dev, sizeof(*region), |