| Message ID | 20210630051118.2212-1-yajun.deng@linux.dev (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: core: Modify alloc_size in alloc_netdev_mqs() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Guessed tree name to be net-next |
| netdev/subject_prefix | warning | Target tree name not specified in the subject |
| netdev/cc_maintainers | success | CCed 10 of 10 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 44 this patch: 44 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 25 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 37 this patch: 37 |
| netdev/header_inline | success | Link |
On Wed, Jun 30, 2021 at 7:11 AM Yajun Deng <yajun.deng@linux.dev> wrote: > > Use ALIGN for 'struct net_device', and remove the unneeded > 'NETDEV_ALIGN - 1'. This can save a few bytes. and modify > the pr_err content when txqs < 1. I think that in old times (maybe still today), SLAB debugging could lead to not unaligned allocated zones. The forced alignment for netdev structures came in commit f346af6a27c0cea99522213cb813fd30489136e2 ("net_device and netdev private struct allocation improvements.") in linux-2.6.3 (back in 2004) This supposedly was a win in itself, otherwise Al Viro would not have spent time on this. > > Signed-off-by: Yajun Deng <yajun.deng@linux.dev> > --- > net/core/dev.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/net/core/dev.c b/net/core/dev.c > index c253c2aafe97..c42a682a624d 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -10789,7 +10789,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, > BUG_ON(strlen(name) >= sizeof(dev->name)); > > if (txqs < 1) { > - pr_err("alloc_netdev: Unable to allocate device with zero queues\n"); > + pr_err("alloc_netdev: Unable to allocate device with zero TX queues\n"); > return NULL; > } > > @@ -10798,14 +10798,12 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, > return NULL; > } > > - alloc_size = sizeof(struct net_device); > + /* ensure 32-byte alignment of struct net_device*/ > + alloc_size = ALIGN(sizeof(struct net_device), NETDEV_ALIGN); This is not really needed, because struct net_device is cache line aligned already on SMP builds. > if (sizeof_priv) { > /* ensure 32-byte alignment of private area */ > - alloc_size = ALIGN(alloc_size, NETDEV_ALIGN); > - alloc_size += sizeof_priv; > + alloc_size += ALIGN(sizeof_priv, NETDEV_ALIGN); No longer needed, the private area starts at the end of struct net_device, whose size is a multiple of cache line. Really I doubt this makes sense anymore these days, we have hundreds of structures in the kernel that would need a similar handling if SLAB/SLUB was doing silly things. I would simply do : alloc_size += sizeof_priv; > } > - /* ensure 32-byte alignment of whole construct */ > - alloc_size += NETDEV_ALIGN - 1; > > p = kvzalloc(alloc_size, GFP_KERNEL | __GFP_RETRY_MAYFAIL); > if (!p) > -- > 2.32.0 >
diff --git a/net/core/dev.c b/net/core/dev.c index c253c2aafe97..c42a682a624d 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10789,7 +10789,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, BUG_ON(strlen(name) >= sizeof(dev->name)); if (txqs < 1) { - pr_err("alloc_netdev: Unable to allocate device with zero queues\n"); + pr_err("alloc_netdev: Unable to allocate device with zero TX queues\n"); return NULL; } @@ -10798,14 +10798,12 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, return NULL; } - alloc_size = sizeof(struct net_device); + /* ensure 32-byte alignment of struct net_device*/ + alloc_size = ALIGN(sizeof(struct net_device), NETDEV_ALIGN); if (sizeof_priv) { /* ensure 32-byte alignment of private area */ - alloc_size = ALIGN(alloc_size, NETDEV_ALIGN); - alloc_size += sizeof_priv; + alloc_size += ALIGN(sizeof_priv, NETDEV_ALIGN); } - /* ensure 32-byte alignment of whole construct */ - alloc_size += NETDEV_ALIGN - 1; p = kvzalloc(alloc_size, GFP_KERNEL | __GFP_RETRY_MAYFAIL); if (!p)
Use ALIGN for 'struct net_device', and remove the unneeded 'NETDEV_ALIGN - 1'. This can save a few bytes. and modify the pr_err content when txqs < 1. Signed-off-by: Yajun Deng <yajun.deng@linux.dev> --- net/core/dev.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)