| Message ID | c94fb1b4dcd9a04eff08cf9ba2444c348477e554.1682023416.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] net: dsa: b53: Slightly optimize b53_arl_read() | expand |
On 4/20/2023 1:44 PM, Christophe JAILLET wrote: > When the 'free_bins' bitmap is cleared, it is better to use its full > maximum size instead of only the needed size. > This lets the compiler optimize it because the size is now known at compile > time. B53_ARLTBL_MAX_BIN_ENTRIES is small (i.e. currently 4), so a call to > memset() is saved. > > Also, as 'free_bins' is local to the function, the non-atomic __set_bit() > can also safely be used here. > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> > --- > drivers/net/dsa/b53/b53_common.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c > index 3464ce5e7470..8c55fe0e0747 100644 > --- a/drivers/net/dsa/b53/b53_common.c > +++ b/drivers/net/dsa/b53/b53_common.c > @@ -1627,7 +1627,7 @@ static int b53_arl_read(struct b53_device *dev, u64 mac, > if (ret) > return ret; > > - bitmap_zero(free_bins, dev->num_arl_bins); > + bitmap_zero(free_bins, B53_ARLTBL_MAX_BIN_ENTRIES); That one I am not a big fan, as the number of ARL bins is a function of the switch model, and this illustrates it well. > > /* Read the bins */ > for (i = 0; i < dev->num_arl_bins; i++) { > @@ -1641,7 +1641,7 @@ static int b53_arl_read(struct b53_device *dev, u64 mac, > b53_arl_to_entry(ent, mac_vid, fwd_entry); > > if (!(fwd_entry & ARLTBL_VALID)) { > - set_bit(i, free_bins); > + __set_bit(i, free_bins); I would be keen on taking that hunk but keep the other as-is. Does that work for you? -- Florian
Le 21/04/2023 à 02:40, Florian Fainelli a écrit : > > > On 4/20/2023 1:44 PM, Christophe JAILLET wrote: >> When the 'free_bins' bitmap is cleared, it is better to use its full >> maximum size instead of only the needed size. >> This lets the compiler optimize it because the size is now known at >> compile >> time. B53_ARLTBL_MAX_BIN_ENTRIES is small (i.e. currently 4), so a >> call to >> memset() is saved. >> >> Also, as 'free_bins' is local to the function, the non-atomic __set_bit() >> can also safely be used here. >> >> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> >> --- >> drivers/net/dsa/b53/b53_common.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/dsa/b53/b53_common.c >> b/drivers/net/dsa/b53/b53_common.c >> index 3464ce5e7470..8c55fe0e0747 100644 >> --- a/drivers/net/dsa/b53/b53_common.c >> +++ b/drivers/net/dsa/b53/b53_common.c >> @@ -1627,7 +1627,7 @@ static int b53_arl_read(struct b53_device *dev, >> u64 mac, >> if (ret) >> return ret; >> - bitmap_zero(free_bins, dev->num_arl_bins); >> + bitmap_zero(free_bins, B53_ARLTBL_MAX_BIN_ENTRIES); > > That one I am not a big fan, as the number of ARL bins is a function of > the switch model, and this illustrates it well. Ok, up to you to take or not what looks the better solution. From my point of view, the "for (i = 0; i < dev->num_arl_bins" below illustrates it better. Maybe, another approach to save the memset() call would be remove the bitmap_zero() call, and declare 'free_bins' as: DECLARE_BITMAP(free_bins, B53_ARLTBL_MAX_BIN_ENTRIES) = { }; (this syntax is already used in b53_configure_vlan()) The compiler should still be able to optimize the initialisation and this wouldn't, IMHO, introduce confusion about the intent. Let me know if you prefer to leave this hunk as-is, or if this other alternative pleases you. CJ > >> /* Read the bins */ >> for (i = 0; i < dev->num_arl_bins; i++) { >> @@ -1641,7 +1641,7 @@ static int b53_arl_read(struct b53_device *dev, >> u64 mac, >> b53_arl_to_entry(ent, mac_vid, fwd_entry); >> if (!(fwd_entry & ARLTBL_VALID)) { >> - set_bit(i, free_bins); >> + __set_bit(i, free_bins); > > I would be keen on taking that hunk but keep the other as-is. Does that > work for you? > -- > Florian >
diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c index 3464ce5e7470..8c55fe0e0747 100644 --- a/drivers/net/dsa/b53/b53_common.c +++ b/drivers/net/dsa/b53/b53_common.c @@ -1627,7 +1627,7 @@ static int b53_arl_read(struct b53_device *dev, u64 mac, if (ret) return ret; - bitmap_zero(free_bins, dev->num_arl_bins); + bitmap_zero(free_bins, B53_ARLTBL_MAX_BIN_ENTRIES); /* Read the bins */ for (i = 0; i < dev->num_arl_bins; i++) { @@ -1641,7 +1641,7 @@ static int b53_arl_read(struct b53_device *dev, u64 mac, b53_arl_to_entry(ent, mac_vid, fwd_entry); if (!(fwd_entry & ARLTBL_VALID)) { - set_bit(i, free_bins); + __set_bit(i, free_bins); continue; } if ((mac_vid & ARLTBL_MAC_MASK) != mac)
When the 'free_bins' bitmap is cleared, it is better to use its full maximum size instead of only the needed size. This lets the compiler optimize it because the size is now known at compile time. B53_ARLTBL_MAX_BIN_ENTRIES is small (i.e. currently 4), so a call to memset() is saved. Also, as 'free_bins' is local to the function, the non-atomic __set_bit() can also safely be used here. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- drivers/net/dsa/b53/b53_common.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)