Re: [PATCH bpf-next 2/3] xdp: xdp_umem: replace kmap on vmap for umem map
From: Jonathan Lemon
Date: Tue Aug 13 2019 - 14:33:24 EST
On 13 Aug 2019, at 11:30, Ivan Khoronzhuk wrote:
On Tue, Aug 13, 2019 at 10:42:18AM -0700, Jonathan Lemon wrote:
On 13 Aug 2019, at 3:23, Ivan Khoronzhuk wrote:
For 64-bit there is no reason to use vmap/vunmap, so use
page_address
as it was initially. For 32 bits, in some apps, like in samples
xdpsock_user.c when number of pgs in use is quite big, the kmap
memory can be not enough, despite on this, kmap looks like is
deprecated in such cases as it can block and should be used rather
for dynamic mm.
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
Seems a bit overkill - if not high memory, kmap() falls back
to just page_address(), unlike vmap().
-- Jonathan
So, as kmap has limitation... if I correctly understood, you propose
to avoid macros and do smth like kmap:
void *addr;
if (!PageHighMem(&umem->pgs[i]))
addr = page_address(page);
else
addr = vmap(&umem->pgs[i], 1, VM_MAP, PAGE_KERNEL);
umem->pages[i].addr = addr;
and while unmap
if (!PageHighMem(&umem->pgs[i]))
vunmap(umem->pages[i].addr);
I can try it, and add this in v2 if no objection.
Seems like a reasonable compromise to me.
--
Jonathan
---
net/xdp/xdp_umem.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index a0607969f8c0..907c9019fe21 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -14,7 +14,7 @@
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <linux/idr.h>
-#include <linux/highmem.h>
+#include <linux/vmalloc.h>
#include "xdp_umem.h"
#include "xsk_queue.h"
@@ -167,10 +167,12 @@ void xdp_umem_clear_dev(struct xdp_umem *umem)
static void xdp_umem_unmap_pages(struct xdp_umem *umem)
{
+#if BITS_PER_LONG == 32
unsigned int i;
for (i = 0; i < umem->npgs; i++)
- kunmap(umem->pgs[i]);
+ vunmap(umem->pages[i].addr);
+#endif
}
static void xdp_umem_unpin_pages(struct xdp_umem *umem)
@@ -378,8 +380,14 @@ static int xdp_umem_reg(struct xdp_umem *umem,
struct xdp_umem_reg *mr)
goto out_account;
}
- for (i = 0; i < umem->npgs; i++)
- umem->pages[i].addr = kmap(umem->pgs[i]);
+ for (i = 0; i < umem->npgs; i++) {
+#if BITS_PER_LONG == 32
+ umem->pages[i].addr = vmap(&umem->pgs[i], 1, VM_MAP,
+ PAGE_KERNEL);
+#else
+ umem->pages[i].addr = page_address(umem->pgs[i]);
+#endif
+ }
return 0;
--
2.17.1
--
Regards,
Ivan Khoronzhuk