Re: [PATCH 08/15] drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
On 07/31/2015 12:20 PM, Viresh Kumar wrote:
On 31-07-15, 11:04, Murali Karicheri wrote:
On 07/31/2015 04:38 AM, Viresh Kumar wrote:
IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
is no need to do that again from its callers. Drop it.
IS_ERR_OR_NULL() is defined as
static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
{
return !ptr || IS_ERR_VALUE((unsigned long)ptr);
}
So the unlikely() applies only to second part. Wouldn't that be a
problem for optimization?
This is what the first patch of the series does:
http://permalink.gmane.org/gmane.linux.kernel/2009151
Assuming the above change is merged, this patch looks good.
Acked-by: Murali Karicheri
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Murali Karicheri
Linux Kernel, Keystone
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Re: [PATCH 08/15] drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
On 31-07-15, 11:04, Murali Karicheri wrote:
> On 07/31/2015 04:38 AM, Viresh Kumar wrote:
> >IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
> >is no need to do that again from its callers. Drop it.
> >
>
> IS_ERR_OR_NULL() is defined as
>
> static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
> {
> return !ptr || IS_ERR_VALUE((unsigned long)ptr);
> }
>
> So the unlikely() applies only to second part. Wouldn't that be a
> problem for optimization?
This is what the first patch of the series does:
http://permalink.gmane.org/gmane.linux.kernel/2009151
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viresh
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RE: [PATCH 08/15] drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
From: Murali Karicheri
> Sent: 31 July 2015 16:04
> On 07/31/2015 04:38 AM, Viresh Kumar wrote:
> > IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
> > is no need to do that again from its callers. Drop it.
> >
>
> IS_ERR_OR_NULL() is defined as
>
> static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
> {
> return !ptr || IS_ERR_VALUE((unsigned long)ptr);
> }
>
> So the unlikely() applies only to second part. Wouldn't that be a
> problem for optimization?
Ugg...
The unlikely() in IS_ERR_VALUE() is likely to stop the compiler
doing a single 'window' comparison for the range [-MAX_ERROR .. 0].
So you are likely to end up with 2 comparisons.
I suspect that:
return IS_ERR_VALUE((unsigned long)ptr - 1);
would be a much better test.
(Ignoring the off-by-one for the highest error.)
David
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Re: [PATCH 08/15] drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
On 07/31/2015 04:38 AM, Viresh Kumar wrote:
IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
is no need to do that again from its callers. Drop it.
IS_ERR_OR_NULL() is defined as
static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
{
return !ptr || IS_ERR_VALUE((unsigned long)ptr);
}
So the unlikely() applies only to second part. Wouldn't that be a
problem for optimization?
Murali
Signed-off-by: Viresh Kumar
---
drivers/net/ethernet/ti/netcp_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/ti/netcp_core.c
b/drivers/net/ethernet/ti/netcp_core.c
index ec8ed30196f3..f685a19a3703 100644
--- a/drivers/net/ethernet/ti/netcp_core.c
+++ b/drivers/net/ethernet/ti/netcp_core.c
@@ -1016,7 +1016,7 @@ netcp_tx_map_skb(struct sk_buff *skb, struct netcp_intf
*netcp)
}
desc = knav_pool_desc_get(netcp->tx_pool);
- if (unlikely(IS_ERR_OR_NULL(desc))) {
+ if (IS_ERR_OR_NULL(desc)) {
dev_err(netcp->ndev_dev, "out of TX desc\n");
dma_unmap_single(dev, dma_addr, pkt_len, DMA_TO_DEVICE);
return NULL;
@@ -1049,7 +1049,7 @@ netcp_tx_map_skb(struct sk_buff *skb, struct netcp_intf
*netcp)
}
ndesc = knav_pool_desc_get(netcp->tx_pool);
- if (unlikely(IS_ERR_OR_NULL(ndesc))) {
+ if (IS_ERR_OR_NULL(ndesc)) {
dev_err(netcp->ndev_dev, "out of TX desc for frags\n");
dma_unmap_page(dev, dma_addr, buf_len, DMA_TO_DEVICE);
goto free_descs;
--
Murali Karicheri
Linux Kernel, Keystone
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[PATCH 08/15] drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
is no need to do that again from its callers. Drop it.
Signed-off-by: Viresh Kumar
---
drivers/net/ethernet/ti/netcp_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/ti/netcp_core.c
b/drivers/net/ethernet/ti/netcp_core.c
index ec8ed30196f3..f685a19a3703 100644
--- a/drivers/net/ethernet/ti/netcp_core.c
+++ b/drivers/net/ethernet/ti/netcp_core.c
@@ -1016,7 +1016,7 @@ netcp_tx_map_skb(struct sk_buff *skb, struct netcp_intf
*netcp)
}
desc = knav_pool_desc_get(netcp->tx_pool);
- if (unlikely(IS_ERR_OR_NULL(desc))) {
+ if (IS_ERR_OR_NULL(desc)) {
dev_err(netcp->ndev_dev, "out of TX desc\n");
dma_unmap_single(dev, dma_addr, pkt_len, DMA_TO_DEVICE);
return NULL;
@@ -1049,7 +1049,7 @@ netcp_tx_map_skb(struct sk_buff *skb, struct netcp_intf
*netcp)
}
ndesc = knav_pool_desc_get(netcp->tx_pool);
- if (unlikely(IS_ERR_OR_NULL(ndesc))) {
+ if (IS_ERR_OR_NULL(ndesc)) {
dev_err(netcp->ndev_dev, "out of TX desc for frags\n");
dma_unmap_page(dev, dma_addr, buf_len, DMA_TO_DEVICE);
goto free_descs;
--
2.4.0
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