| Message ID | 20211207030750.30824-3-bhe@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Avoid requesting page from DMA zone when no managed pages | expand |
On 12/6/21 9:07 PM, Baoquan He wrote: > In the current code, three atomic memory pools are always created, > atomic_pool_kernel|dma|dma32, even though 'coherent_pool=0' is > specified in kernel command line. In fact, atomic pool is only > necessary when CONFIG_DMA_DIRECT_REMAP=y or mem_encrypt_active=y > which are needed on few ARCHes. > > So change code to allow user to disable atomic pool by specifying > 'coherent_pool=0'. > > Meanwhile, update the relevant document in kernel-parameter.txt. > > Signed-off-by: Baoquan He <bhe@redhat.com> Reviewed-by: John Donnelly <john.p.donnelly@oracle.com> Tested-by: John Donnelly <john.p.donnelly@oracle.com> > --- > Documentation/admin-guide/kernel-parameters.txt | 3 ++- > kernel/dma/pool.c | 7 +++++-- > 2 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index ec4d25e854a8..d7015309614b 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -664,7 +664,8 @@ > > coherent_pool=nn[KMG] [ARM,KNL] > Sets the size of memory pool for coherent, atomic dma > - allocations. Otherwise the default size will be scaled > + allocations. A value of 0 disables the three atomic > + memory pool. Otherwise the default size will be scaled > with memory capacity, while clamped between 128K and > 1 << (PAGE_SHIFT + MAX_ORDER-1). > > diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c > index 5f84e6cdb78e..5a85804b5beb 100644 > --- a/kernel/dma/pool.c > +++ b/kernel/dma/pool.c > @@ -21,7 +21,7 @@ static struct gen_pool *atomic_pool_kernel __ro_after_init; > static unsigned long pool_size_kernel; > > /* Size can be defined by the coherent_pool command line */ > -static size_t atomic_pool_size; > +static unsigned long atomic_pool_size = -1; > > /* Dynamic background expansion when the atomic pool is near capacity */ > static struct work_struct atomic_pool_work; > @@ -188,11 +188,14 @@ static int __init dma_atomic_pool_init(void) > { > int ret = 0; > > + if (!atomic_pool_size) > + return 0; > + > /* > * If coherent_pool was not used on the command line, default the pool > * sizes to 128KB per 1GB of memory, min 128KB, max MAX_ORDER-1. > */ > - if (!atomic_pool_size) { > + if (atomic_pool_size == -1) { > unsigned long pages = totalram_pages() / (SZ_1G / SZ_128K); > pages = min_t(unsigned long, pages, MAX_ORDER_NR_PAGES); > atomic_pool_size = max_t(size_t, pages << PAGE_SHIFT, SZ_128K); >
On Tue, Dec 07, 2021 at 11:07:47AM +0800, Baoquan He wrote: > In the current code, three atomic memory pools are always created, > atomic_pool_kernel|dma|dma32, even though 'coherent_pool=0' is > specified in kernel command line. In fact, atomic pool is only > necessary when CONFIG_DMA_DIRECT_REMAP=y or mem_encrypt_active=y > which are needed on few ARCHes. And only these select the atomic pool, so it won't get created otherwise. What problem are you trying to solve?
On 12/13/21 at 08:44am, Christoph Hellwig wrote: > On Tue, Dec 07, 2021 at 11:07:47AM +0800, Baoquan He wrote: > > In the current code, three atomic memory pools are always created, > > atomic_pool_kernel|dma|dma32, even though 'coherent_pool=0' is > > specified in kernel command line. In fact, atomic pool is only > > necessary when CONFIG_DMA_DIRECT_REMAP=y or mem_encrypt_active=y > > which are needed on few ARCHes. > > And only these select the atomic pool, so it won't get created otherwise. > What problem are you trying to solve? This tries to make "coherent_pool=0" behave normally. As you see, 'coherent_pool=0' will behave like no 'coherent_pool' being specified. This is not consistent with other similar kernel parameter, e.g cma=. At the beginning, I planned to add a knob to allow user to disable one or all atomic pool. Later I changed. However I think this patch makes sense on fixing the a little bizarre behaviour, 'coherent_pool=0' but still get atomic pool created. I can drop it if you think it's unnecessary.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ec4d25e854a8..d7015309614b 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -664,7 +664,8 @@ coherent_pool=nn[KMG] [ARM,KNL] Sets the size of memory pool for coherent, atomic dma - allocations. Otherwise the default size will be scaled + allocations. A value of 0 disables the three atomic + memory pool. Otherwise the default size will be scaled with memory capacity, while clamped between 128K and 1 << (PAGE_SHIFT + MAX_ORDER-1). diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c index 5f84e6cdb78e..5a85804b5beb 100644 --- a/kernel/dma/pool.c +++ b/kernel/dma/pool.c @@ -21,7 +21,7 @@ static struct gen_pool *atomic_pool_kernel __ro_after_init; static unsigned long pool_size_kernel; /* Size can be defined by the coherent_pool command line */ -static size_t atomic_pool_size; +static unsigned long atomic_pool_size = -1; /* Dynamic background expansion when the atomic pool is near capacity */ static struct work_struct atomic_pool_work; @@ -188,11 +188,14 @@ static int __init dma_atomic_pool_init(void) { int ret = 0; + if (!atomic_pool_size) + return 0; + /* * If coherent_pool was not used on the command line, default the pool * sizes to 128KB per 1GB of memory, min 128KB, max MAX_ORDER-1. */ - if (!atomic_pool_size) { + if (atomic_pool_size == -1) { unsigned long pages = totalram_pages() / (SZ_1G / SZ_128K); pages = min_t(unsigned long, pages, MAX_ORDER_NR_PAGES); atomic_pool_size = max_t(size_t, pages << PAGE_SHIFT, SZ_128K);
In the current code, three atomic memory pools are always created, atomic_pool_kernel|dma|dma32, even though 'coherent_pool=0' is specified in kernel command line. In fact, atomic pool is only necessary when CONFIG_DMA_DIRECT_REMAP=y or mem_encrypt_active=y which are needed on few ARCHes. So change code to allow user to disable atomic pool by specifying 'coherent_pool=0'. Meanwhile, update the relevant document in kernel-parameter.txt. Signed-off-by: Baoquan He <bhe@redhat.com> --- Documentation/admin-guide/kernel-parameters.txt | 3 ++- kernel/dma/pool.c | 7 +++++-- 2 files changed, 7 insertions(+), 3 deletions(-)