linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Dongli Zhang <dongli.zhang@oracle.com>
To: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Cc: konrad.wilk@oracle.com, hch@lst.de, m.szyprowski@samsung.com,
	robin.murphy@arm.com, joe.jin@oracle.com,
	dongli.zhang@oracle.com
Subject: [PATCH RFC 1/1] swiotlb: add debugfs to track swiotlb buffer usage
Date: Thu,  6 Dec 2018 11:59:45 +0800	[thread overview]
Message-ID: <1544068785-20399-1-git-send-email-dongli.zhang@oracle.com> (raw)

The device driver will not be able to do dma operations once swiotlb buffer
is full, either because the driver is using so many IO TLB blocks inflight,
or because there is memory leak issue in device driver. To export the
swiotlb buffer usage via debugfs would help the user estimate the size of
swiotlb buffer to pre-allocate or analyze device driver memory leak issue.

As the swiotlb can be initialized at very early stage when debugfs cannot
register successfully, this patch creates the debugfs entry on demand.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
 kernel/dma/swiotlb.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 045930e..d3c8aa4 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -35,6 +35,9 @@
 #include <linux/scatterlist.h>
 #include <linux/mem_encrypt.h>
 #include <linux/set_memory.h>
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+#endif
 
 #include <asm/io.h>
 #include <asm/dma.h>
@@ -73,6 +76,13 @@ static phys_addr_t io_tlb_start, io_tlb_end;
  */
 static unsigned long io_tlb_nslabs;
 
+#ifdef CONFIG_DEBUG_FS
+/*
+ * The number of used IO TLB block
+ */
+static unsigned long io_tlb_used;
+#endif
+
 /*
  * This is a free list describing the number of free entries available from
  * each index
@@ -100,6 +110,41 @@ static DEFINE_SPINLOCK(io_tlb_lock);
 
 static int late_alloc;
 
+#ifdef CONFIG_DEBUG_FS
+
+static struct dentry *d_swiotlb_usage;
+
+static int swiotlb_usage_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%lu\n%lu\n", io_tlb_used, io_tlb_nslabs);
+	return 0;
+}
+
+static int swiotlb_usage_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, swiotlb_usage_show, NULL);
+}
+
+static const struct file_operations swiotlb_usage_fops = {
+	.open           = swiotlb_usage_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+void swiotlb_create_debugfs(void)
+{
+	d_swiotlb_usage = debugfs_create_dir("swiotlb", NULL);
+
+	if (!d_swiotlb_usage)
+		return;
+
+	debugfs_create_file("usage", 0600, d_swiotlb_usage,
+			    NULL, &swiotlb_usage_fops);
+}
+
+#endif
+
 static int __init
 setup_io_tlb_npages(char *str)
 {
@@ -449,6 +494,11 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
 		pr_warn_once("%s is active and system is using DMA bounce buffers\n",
 			     sme_active() ? "SME" : "SEV");
 
+#ifdef CONFIG_DEBUG_FS
+	if (unlikely(!d_swiotlb_usage))
+		swiotlb_create_debugfs();
+#endif
+
 	mask = dma_get_seg_boundary(hwdev);
 
 	tbl_dma_addr &= mask;
@@ -528,6 +578,9 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
 		dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size);
 	return SWIOTLB_MAP_ERROR;
 found:
+#ifdef CONFIG_DEBUG_FS
+	io_tlb_used += nslots;
+#endif
 	spin_unlock_irqrestore(&io_tlb_lock, flags);
 
 	/*
@@ -588,6 +641,10 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
 		 */
 		for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
 			io_tlb_list[i] = ++count;
+
+#ifdef CONFIG_DEBUG_FS
+		io_tlb_used -= nslots;
+#endif
 	}
 	spin_unlock_irqrestore(&io_tlb_lock, flags);
 }
-- 
2.7.4


             reply	other threads:[~2018-12-06  3:58 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-06  3:59 Dongli Zhang [this message]
2018-12-06 16:12 ` [PATCH RFC 1/1] swiotlb: add debugfs to track swiotlb buffer usage Joe Jin
2018-12-07  5:49   ` Dongli Zhang
2018-12-07  6:33     ` Joe Jin
2018-12-07 13:17     ` Robin Murphy
2018-12-09  1:37       ` Dongli Zhang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1544068785-20399-1-git-send-email-dongli.zhang@oracle.com \
    --to=dongli.zhang@oracle.com \
    --cc=hch@lst.de \
    --cc=iommu@lists.linux-foundation.org \
    --cc=joe.jin@oracle.com \
    --cc=konrad.wilk@oracle.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=m.szyprowski@samsung.com \
    --cc=robin.murphy@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).